gracefully handle ExitStatus exception in async main loops
 - added readFile and writeFile helpers
 - added default modes to mkdir / mkdev
updated unistd and fs_base tests to use new FS APIs
Single quotes for cDefine.
Remove unused / unwritten emlibtool.

This isn't used or even implemented and apparently isn't necessary.
rearranged FS function order
Improve precision of clock_gettime(). Update clock_getres().
Merge pull request #1592 from waywardmonkeys/additional-clock-gettime-precision

Additional clock_gettime precision
Merge pull request #1585 from waywardmonkeys/single-quotes-for-cdefine

Single quotes for cdefine
Merge pull request #1593 from juj/TEMP_DIR_check

Temp dir check
Merge pull request #1586 from waywardmonkeys/remove-emlibtool

Remove emlibtool
add long double aliases for a lot of things.

__fpclassify and __signbit are handled in another patch on the
libc header replacement branch.
Merge pull request #1595 from waywardmonkeys/whole-lotta-long-double-loving

A whole lotta long double loving
double simplifications
Merge pull request #1581 from inolen/rwfile

added read/writeFile helpers, updated tests to use new FS APIs
Use __EMSCRIPTEN__ rather than EMSCRIPTEN.

This was requested by someone upstream when I'd originally submitted
these changes and is more correct.
fix inline js in x86 target, enable testing sans validation for inline js in asm.js, fix unistd tests that use inline js to not validate, and make js optimizer more tolerant of inline js in asm code; fixes #1597
improve non-switchification error message
Merge pull request #1596 from waywardmonkeys/change-preprocessor-define-libcxx

Change preprocessor define libcxx
Merge pull request #1598 from juj/informative_oom_message

Informative oom message