add wrapper headers, with warnings, for various incorrect names under sys

also add a warning to the existing sys/poll.h. the warning is absent
from sys/dir.h because it is actually providing a slightly different
API to the program, and thus just replacing the #include directive is
not a valid fix to programs using this one.
reorder strftime to eliminate the incorrect indention level

this change is in preparation for possibly adding support for the
field width and padding specifiers added in POSIX 2008.
fix indention-with-spaces
fix semantically incorrect use of LC_GLOBAL_LOCALE

LC_GLOBAL_LOCALE refers to the global locale, controlled by setlocale,
not the thread-local locale in effect which these functions should be
using. neither LC_GLOBAL_LOCALE nor 0 has an argument to the *_l
functions has behavior defined by the standard, but 0 is a more
logical choice for requesting the callee to lookup the current locale.
in the future I may move the current locale lookup the the caller (the
non-_l-suffixed wrapper).

at this point, all of the locale logic is dummied out, so no harm was
done, but it should at least avoid misleading usage.
add missing erfcl wrapper for archs where long double is plain double
release notes for 0.9.12
use separate sigaction buffers for old and new data

in signal() it is needed since __sigaction uses restrict in parameters
and sharing the buffer is technically an aliasing error. do the same
for the syscall, as at least qemu-user does not handle it properly.
fix some prctl macros that were incorrectly copied into this file
add macros for new(ish) prctl commands
don't call null pointer if DT_INIT/DT_FINI are null

it's not clear to me why the linker even outputs these headers if they
are null, but apparently it does so. with the default startfiles, they
will never be null anyway, but this patch allows eliminating crti,
crtn, crtbegin, and crtend (leaving only crt1) if the toolchain is
using init_array/fini_array (or for a C-only, no-ctor environment).
fix bug where read error was treated as success reading library headers
add some sanity checks in dynamic loader code

reject elf files which are not ET_EXEC/ET_DYN type as bad exec format,
and reject ET_EXEC files when they cannot be loaded at the correct
address, since they are not relocatable at runtime. the main practical
benefit of this is to make dlopen of the main program fail rather than
producing an unsafe-to-use handle.
prevent passing PT_INTERP name to dlopen from double-loading libc

the dev/inode for the main app and the dynamic linker ("interpreter")
are not available, so the subsequent checks don't work. in general we
don't want to make exact string matches to existing libraries prevent
loading new ones, since this breaks loading upgraded modules in
module-loading systems. so instead, special-case it.

the motivation for this fix is that calling dlopen on the names
returned by dl_iterate_phdr or walking the link map (obtained by
dlinfo) seem to be the only methods available to an application to
actually get a list of open dso handles.
fix theoretical out-of-bound access in dynamic linker

one of the arguments to memcmp may be shorter than the length l-3, and
memcmp is under no obligation not to access past the first byte that
differs. instead use strncmp which conveys the correct semantics. the
performance difference is negligible here and since the code is only
use for shared libc, both functions are already linked anyway.
in pthread_getattr_np, use mremap rather than madvise to measure stack

the original motivation for this patch was that qemu (and possibly
other syscall emulators) nop out madvise, resulting in an infinite
loop. however, there is another benefit to this change: madvise may
actually undo an explicit madvise the application intended for its
stack, whereas the mremap operation is a true nop. the logic here is
that mremap must fail if it cannot resize the mapping in-place, and
the caller knows that it cannot resize in-place because it knows the
next page of virtual memory is already occupied.
work around gcc 4.8's generation of self-referential mem* functions at -O3
optimized memset asm for i386 and x86_64

the concept of both versions is the same; they differ only in details.
for long runs, they use "rep movsl" or "rep movsq", and for small
runs, they use a trick, writing from both ends towards the middle,
that reduces the number of branches needed. in addition, if memset is
called multiple times with the same length, all branches will be
predicted; there are no loops.

for larger runs, there are likely faster approaches than "rep", at
least on some cpu models. for 32-bit, it's unlikely that there is any
faster approach that does not require non-baseline instructions; doing
anything fancier would require inspecting cpu capabilities. for
64-bit, there may very well be faster versions that work on all
models; further optimization could be explored in the future.

with these changes, memset is anywhere between 50% faster and 6 times
faster, depending on the cpu model and the length and alignment of the
destination buffer.
make mkdtemp and mkstemp family leave template unchanged on fail

also refactor mkdtemp based on new shared temp code, removing
dependency on the deprecated mktemp, whose behavior made this logic
more difficult.
remove (no longer useful) namespace-protected __mktemp symbol
fix (deprecated) mktemp logic and update it to match other temp functions

the access function cannot be used to check for existence, because it
operates using real uid/gid rather than effective to determine
accessibility; this matters for the non-final path components.
instead, use stat. failure of stat is success if only the final
component is missing (ENOENT) and otherwise is failure.