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
add threadasm.S to win64.mak MANIFEST
Merge pull request #364 from dawgfoto/MIPS

MIPS port
Merge branch 'master' of https://github.com/D-Programming-Language/druntime into dmd-master