fix for broken kernel side RLIM_INFINITY on mips

On 32 bit mips the kernel uses -1UL/2 to mark RLIM_INFINITY (and
this is the definition in the userspace api), but since it is in
the middle of the valid range of limits and limits are often
compared with relational operators, various kernel side logic is
broken if larger than -1UL/2 limits are used. So we truncate the
limits to -1UL/2 in get/setrlimit and prlimit.

Even if the kernel side logic consistently treated -1UL/2 as greater
than any other limit value, there wouldn't be any clean workaround
that allowed using large limits:
* using -1UL/2 as RLIM_INFINITY in userspace would mean different
infinity value for get/setrlimt and prlimit (where infinity is always
-1ULL) and userspace logic could break easily (just like the kernel
is broken now) and more special case code would be needed for mips.
* translating -1UL/2 kernel side value to -1ULL in userspace would
mean that -1UL/2 limit cannot be set (eg. -1UL/2+1 had to be passed
to the kernel instead).
fix breakage from recent syscall commits due to missing errno macros
add sched_{get,set}attr syscall numbers and SCHED_DEADLINE macro

linux 3.14 introduced sched_getattr and sched_setattr syscalls in
commit d50dde5a10f305253cbc3855307f608f8a3c5f73

and the related SCHED_DEADLINE scheduling policy in
commit aab03e05e8f7e26f51dee792beddcb5cca9215a5

but struct sched_attr "extended scheduling parameters data structure"
is not yet exported to userspace (necessary for using the syscalls)
so related uapi definitions are not added yet.
add SO_BPF_EXTENSIONS socket option

this was introduced to query BPF extension support with getsockopt
in linux 3.14, commit ea02f9411d9faa3553ed09ce0ec9f00ceae9885e
update netinet/in.h to match the current kernel uapi

from linux/in.h and linux/in6.h uapi headers the following
missing socket options were added:

IP_NODEFRAG - used with customized ipv4 headers
IPV6_RECVPATHMTU - for ipv6 path mtu
IPV6_PATHMTU - for ipv6 path mtu
IPV6_DONTFRAG - for ipv6 path mtu
IPV6_ADDR_PREFERENCES - RFC5014 Source Address Selection
IPV6_MINHOPCOUNT - RFC5082 Generalized TTL Security Mechanism
IPV6_ORIGDSTADDR - used by tproxy
IPV6_RECVORIGDSTADDR - used by tproxy
IPV6_TRANSPARENT - used by tproxy
IPV6_UNICAST_IF - ipv6 version of IP_UNICAST_IF

and socket option values:

IP_PMTUDISC_OMIT - value for IP_MTU_DISCOVER option, new in linux 3.14
IPV6_PMTUDISC_OMIT - same for IPV6_MTU_DISCOVER
IPV6_PMTUDISC_INTERFACE - ipv6 version of IP_PMTUDISC_INTERFACE
IPV6_PREFER_* - flags for IPV6_ADDR_PREFERENCES

not added: ipv6 flow info and flow label related definitions.
(it's unclear if libc should define these and namespace polluting
type name is involved so they are not provided for now)
use cleaner code for handling float rounding in vfprintf

CONCAT(0x1p,LDBL_MANT_DIG) is not safe outside of libc,
use 2/LDBL_EPSILON instead.

fix was proposed by Morten Welinder.
fix POSIX namespace pollution in sys/types.h

int8_t, u_int8_t, etc types are moved under _BSD_SOURCE
refactor getaddrinfo and add support for most remaining features

this is the first phase of the "resolver overhaul" project.

conceptually, the results of getaddrinfo are a direct product of a
list of address results and a list of service results. the new code
makes this explicit by computing these lists separately and combining
the results. this adds support for services that have both tcp and udp
versions, where the caller has not specified which it wants, and
eliminates a number of duplicate code paths which were all producing
the final output addrinfo structures, but in subtly different ways,
making it difficult to implement any of the features which were
missing.

in addition to the above benefits, the refactoring allows for legacy
functions like gethostbyname to be implemented without using the
getaddrinfo function itself. such changes to the legacy functions have
not yet been made, however.

further improvements include matching of service alias names from
/etc/services (previously only the primary name was supported),
returning multiple results from /etc/hosts (previously only the first
matching line was honored), and support for the AI_V4MAPPED and AI_ALL
flags.

features which remain unimplemented are IDN translations (encoding
non-ASCII hostnames for DNS lookup) and the AI_ADDRCONFIG flag.

at this point, the DNS-based name resolving code is still based on the
old interfaces in __dns.c, albeit somewhat simpler in its use of them.
there may be some dead code which could already be removed, but
changes to this layer will be a later phase of the resolver overhaul.
improve gethostbyname2_r using new resolver backend

these changes reduce the size of the function somewhat and remove many
of its dependencies, including free. in principle it should now be
async-signal-safe, but this has not been verified in detail.

minor changes to error handling are also made.
improve getservbyname_r using new resolver backend

now that host and service lookup have been separated in the backend,
there's no need for service lookup functions to pull in the host
lookup code. moreover, dynamic allocation is no longer needed, so this
function should now be async-signal-safe. it's also significantly
smaller.

one change in getservbyname is also made: knowing that getservbyname_r
needs only two character pointers in the caller-provided buffer, some
wasted bss can be avoided.
fix off-by-one in checking hostname length in new resolver backend

this bug was introduced in the recent resolver overhaul commits. it
likely had visible symptoms. these were probably limited to wrongly
accepting truncated versions of over-long names (vs rejecting them),
as opposed to stack-based overflows or anything more severe, but no
extensive checks were made. there have been no releases where this bug
was present.
add ipsec and tunneling protocols to getprotoent-family functions

iptables and ipsec-tools among others require these to function
properly.
implement new dns backend, res_send and other legacy resolver functions

this is the second phase of the "resolver overhaul" project.

the key additions in this commit are the __res_msend and __res_mkquery
functions, which have been factored so as to provide a backend for
both the legacy res_* functions and the standard getaddrinfo and
getnameinfo functions. the latter however are still using the old
backend code; there is code duplication which still needs to be
removed, and this will be the next phase of the resolver overhaul.

__res_msend is derived from the old __dns_doqueries function, but
generalized to send arbitrary caller-provided packets in parallel
rather than producing the parallel queries itself. this allows it to
be used (completely trivially) as a backend for res_send. the
factored-out query generation code, with slightly more generality, is
now part of __res_mkquery.
fix uninitialized variable in new __res_msend dns function
switch standard resolver functions to use the new dns backend

this is the third phase of the "resolver overhaul" project.

this commit removes all of the old dns code, and switches the
__lookup_name backend (used by getaddrinfo, etc.) and the getnameinfo
function to use the newly implemented __res_mkquery and __res_msend
interfaces. for parsing the results, a new callback-based __dns_parse
function, based on __dns_get_rr from the old dns code, is used.
remove cruft from old resolver and numeric ip parsing

the old resolver code used a function __ipparse which contained the
logic for inet_addr and inet_aton, which is needed in getaddrinfo.
this was phased out in the resolver overhaul in favor of directly
using inet_aton and inet_pton as appropriate.

this commit cleans up some stuff that was left behind.
fix incorrect end pointer in some cases when wcsrtombs stops early

when wcsrtombs stopped due to hitting zero remaining space in the
output buffer, it was wrongly clearing the position pointer as if it
had completed the conversion successfully.

this commit rearranges the code somewhat to make a clear separation
between the cases of ending due to running out of output buffer space,
and ending due to reaching the end of input or an illegal sequence in
the input. the new branches have been arranged with the hope of
optimizing more common cases, too.
fix some validation checks in dns response parsing code

since the buffer passed always has an actual size of 512 bytes, the
maximum possible response packet size, no out-of-bounds access was
possible; however, reading past the end of the valid portion of the
packet could cause the parser to attempt to process junk as answer
content.
fix negative response and non-response handling for dns queries

previously, all failures to obtain at least one address were treated
as nonexistant names (EAI_NONAME). this failed to account for the
possibility of transient failures (no response at all, or a response
with rcode of 2, server failure) or permanent failures that do not
indicate the nonexistence of the requested name. only an rcode of 3
should be treated as an indication of nonexistence.
fix if_nametoindex return value when interface does not exist

the return value is unsigned, so negative results for "errors" do not
make sense; 0 is the value reserved for when the interface name does
not exist.