Note change in signgam implementation from upstream.
Fix asm2 compilation where __toread was used.
Replace implementation of warn*/err*.

This eliminates a large number of warnings about incompatible function pointer
casts when compiling for asm.js.
stdlib/strtod.c is no longer used.

This has been replaced with code from musl.
Replace getopt_long with musl version.
Move err/warn/etc from libc to libcextra.
Expand aliases for strto*_l() to short functions.

This removes warnings about incompatible pointer types in asm2 mode.
Bump version.
Add GLEW 1.10.0 emulation

Includes library_glew.js that stubs the init functions, but also provides the
other functions.

GL/glew.h is now changed to work with GLEW_EXT_foo_bar constants,
some missing constants that are in GLEW 1.10.0 are also provided.

Otherwise it still uses SDL_opengl.h to provide function definitions and
other constants.

Linaro's GLEW (glew-oes) is also supported to some degree to make it
easier to get ES1 and ES2 software using it running.

What it lacks:
- Some constants and function declarations that are in GLEW 1.10.0
might be missing.
- The real glew-es fork also includes normal GL constants and
function pointers, this does not.

Tests ran:
- tests/runner.py browser

Real world example using this code (and upcomming glfw3 port) can be found here:
http://cloudef.eu/glhck
http://cloudef.eu/glhck/qb.html
Merge pull request #1878 from Cloudef/incoming

Add GLEW 1.10.0 emulation
Merge pull request #2009 from waywardmonkeys/updates2

Updates2
fix double start bug #1992 in browser as well
disable test_simd3 due to breakage
fix wprintf-related bug that bit fastcomp
fix for running js optimizer standalone
fix aggressiveVariableElimination bug and add testing
Fill in undefined math symbols.
Bump version.
Further optimize FFP GL getRenderer() operation.
Optimize rendering from client-side memory by maintaining a set of doublebuffered VBOs. This improves performance by reducing CPU-GPU pipeline stalls.