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
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.