implement pthread_getattr_np

this function is mainly (purely?) for obtaining stack address
information, but we also provide the detach state since it's easy to
do anyway.
provide prototype for pthread_getattr_np
fix typo in setpriority syscall wrapper
add new linux tcp socket option flags to netinet/tcp.h
add ADJ_SETOFFSET timex mode bit (new in linux v2.6.39)
adding ethernet protocol ids to if_ether.h following linux
add new socket options to sys/socket.h following linux
add the new SO_REUSEPORT socket option to mips and powerpc

SO_REUSEPORT implementation was merged in the linux kernel commit
c617f398edd4db2b8567a28e899a88f8f574798d 2013-01-23
add syscall numbers for the new kcmp and finit_module syscalls
and remove syscall todos from microblaze
__time_to_tm: initialize tm_zone and tm_gmtoff
make tm_zone etc visible under _GNU_SOURCE
add arpa/nameser_compat.h

the contents of this header are already in arpa/nameser.h
re-add useconds_t

this type was removed back in 5243e5f1606a9c6fcf01414e ,
because it was removed from the XSI specs.
however some apps use it.
since it's in the POSIX reserved namespace, we can expose it
unconditionally.
Merge branch 'master' of git://git.musl-libc.org/musl into syscall