Simplify some timezone code.

Since we only allow GMT as a timezone and ignore what the browser
says, we can simplify a lot of this code.
Single quotes for cDefine.
Remove unused / unwritten emlibtool.

This isn't used or even implemented and apparently isn't necessary.
Added test which shows broken GL emulation when:
1. Binding to a VertexObjectBuffer and calling `glDrawArrays` on two
   different sections of it.
2. Using `glVertexPointer` with actual pointer to a vertex array
   and calling `glDrawArrays` on two different sections of it.
Merge branch 'vertex_array_object_bug' of github.com:michaeljbishop/emscripten into incoming
Improve emscripten to autodetect the temp directory even if TEMP_DIR is not present at all in ~/.emscripten. Add sanitation to TEMP_DIR handling to detect that the path exists. Paths like TEMP_DIR='/tmp' and TEMP_DIR='c:\temp' will now print out a descriptive error message on Windows. (proper form is TEMP_DIR='c:\\temp' or TEMP_DIR='c:/temp' on Windows). Fixes #1292.
fix repeated calls to glDraw* where the count changes but not the client attributes; fixes part of #1589
handle glBufferData usages that are not in WebGL; fixes #1589
do not fail in test_dlfcn_qsort of js engine cannot do asm validation; fixes #1591
do not emit externals in side modules
remove no longer needed library.js constants for some libcxxabi stuff, which can confuse INCLUDE_FULL_LIBRARY+exceptions
dlopen+exceptions+asm is not supported yet
longjmp test across asm modules
Merge pull request #1582 from waywardmonkeys/simplify-timezone

Simplify timezone
restore ZTVN10 hacks, but only for non-ta2 where we do not link in libcxxabi
Improve precision of clock_gettime(). Update clock_getres().
Merge pull request #1587 from inolen/openal_buffers_revert

revert pr #1493
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