Some large file support enhancements

The normal functions should be aliases to the *64 functions,
even if _LARGEFILE64_SOURCE is false. _LARGEFILE64_SOURCE is
more or less deprecated.
MIPS specific linux constants

- core.sys.posix.fcntl
- core.sys.posix.signal
- core.sys.posix.sys.mman
- core.sys.posix.sys.socket
port back GDC's __jmp_buf for ARM/PPC/PPC64

- I rechecked glibc's definitions
__jmp_buf for setjmp
ucontext_t
stat_t
Revert "Merge pull request #208 from alexrp/remove-threadasm"

This reverts commit f66067edc21777106e39f16e30eae3b28cc4b156, reversing
changes made to c97b1e9074321f3aa9ea42cd7e91711ac6055e46.
fix noexecstack assembler flag

- "clang -cc1as" only accepts the double dashed version
merge GDC changes to threadasm.S
fiber_switchContext for MIPS_O32
Added core.sys.posix.grp (from Posix <grp.h>).

No Solaris declarations for now.
files missing from manifest
always create zip file
Added core.sys.posix.grp to all make files.
Added XSI prototypes.
Fix a few issues in posix.mak
Remove debug echo
Put the optional prototypes into per-platform version statements.
Merge pull request #374 from andralex/master

Fix a few issues with posix.mak
Added nothrow...