socketpair
Use -target rather than -triple with clang.

Apparently -target replaced -triple in the past. Using -target
also makes the behavior of clang match the target rather than
the host platform.
Remove flags for disabling ms-compatibility.

With the use of -target rather than -triple, these are no longer
needed.
__STDC__ is already defined by clang.
Remove unnecessary x86_64 and x87 undefines.

These aren't defined for our target in the first place, so we
don't need to undefine them.
Remove unnecessary undefine of __CYGWIN__.
be more flexible in check for keeping std* as low values; cttz/ctlz can add 512 bytes to initial allocations
Restore -O2 test on other.test_embind - works ok.
Just return op not supported.

See #1060
setjmp support for asm.js
throw in longjmp, do not overwrite previous throw data in setThrew, and enable test_longjmp in asm
enable test_longjmp4 in asm
exit to caller when setjmp encounters an id that is not ours; enable test_longjmp2 and 3 in asm
enable tests/cases/*longjmp* for asm
Improve error reporting in build_library.
always hardcode arguments in benchmarks
properly clear __THREW__ in asm exceptions
Merge pull request #1079 from juj/build_library_error_report

Improve error reporting in build_library.
Merge pull request #1073 from waywardmonkeys/cleanup-compiler-flags

Cleanup compiler flags
enable ASM_JS=1 in -O1+, and start to update testing