emscripten_get_now enabled for SpiderMonkey, optimization and test for shell and browser.
Formatting.
Update STD*_FILENO constants in settings.js to match unistd.h

They are 1,2,3 in unistd.h (correct) but were 0,1,2 in settings.js, so calling
`cDefine('STDOUT_FILENO')` (for example) would return the incorrect value.

This addresses issue #1570, but not #1408.
Pass relative paths instead of absolute paths in Visual Studio include directories for the glbook samples in msvc10 tests. Fixes #1568.
allow null second param in createPreloadedFile|createDataFile so that file packager does not need PATH, and works through closure
 - added stubs for tcgetattr and tcsetattr
 - added fixes for tty get_char in the node environment
 - added tests for tcgetattr / tcsetattr
 - made test_stdin async to work in the node environment
 - clearerr should reset both eof and error indicators
 - fgetc was incorrectly setting the eof indicator. in cases where fread had errored with EAGAIN it was setting eof. I removed the set entirely, as there is no need for fgetc to even worry about it, fread will set the correct value in any case
updated test_stdin to work in SM shell
run test_stdin in all JS_ENGINES
Merge pull request #1572 from rharkeadsk/fix-stdio-fileno-constants

Fix STD*_FILENO constants in JavaScript to match C
Merge pull request #1555 from inolen/tty_fixes

added stubs for tcgetattr and tcsetattr, minor node tty fixes
Merge pull request #1311 from juj/emscripten_get_now

emscripten_get_now enabled for SpiderMonkey, optimization and test.
Update libc headers to use musl headers.
Fixup libcxx to work with musl includes.
Fix test_zlib. off_t is now 64bit.
Update to work with new libc headers.
Fix other.test_embind & other.test_static_link.
Fix test_time.
Add __va_copy as a compat/stdarg.h
Fix fpclassify with musl libc headers.

musl defines __fpclassify, __fpclassifyf, __fpclassifyl while
the old headers used __fpclassifyd for double rather than
__fpclassify.