Test for va_arg support on struct types (disabled on nested struct)

va_arg is not yet supported on nested struct types (see
https://code.google.com/p/nativeclient/issues/detail?id=3815)
[trace] Fix copy/paste error.
Implement SDL_SetClipRect/SDL_GetClipRect
Merge pull request #2931 from caiiiycuk/sdl_setcliprect

Implement SDL_SetClipRect/SDL_GetClipRect
Merge pull request #2935 from waywardmonkeys/trace-fix

[trace] Fix copy/paste error.
Only replace slashes if the argument is defined

Fixes #2920
Merge pull request #2936 from aidanhs/aphs-fix-nodejs-no-args

Fix 'require' for emscripten modules in nodejs
fix up test_require
experimental option to emit JSON in EMCC_DEBUG=2 interim phases
Merge pull request #2923 from ericrannaud/incoming

Test for va_arg support on struct types (disabled on nested struct)
FS tests should not accumulate FS defines
Implement GLES3 functions:

* glGetActiveUniformBlockName
* glGetActiveUniformBlockiv
* glGetIntegeri_v
* glGetUniformBlockIndex
* glGetUniformIndices
* glUniformBlockBinding
Implement GLES3 Transform Feedbacks.
Make sure zero length reads work in NODEFS

Fixes #2266
Empty ungotten chars for all filesystems when llseeking
Perform fgetc/ungetc test on both MEMFS and NODEFS
fix other.test_require
sdl_image version 3
Merge pull request #2939 from aidanhs/aphs-test-only-one-fs

Make tests of different filesystems actually test the different filesystems
Merge pull request #2942 from djg/webgl2-transformfeedbacks

Implement GLES3 Transform Feedbacks