add support for WebGL hardware instancing through extension ANGLE_instanced_arrays
use GL_ASSERTIONS instead of ASSERTIONS
add OpenGL Desktop/ES 2.0 hardware instancing extensions compatibility functions
Fix missing SDL_LockSurface reference

Prior to this change, when blitting from the screen to a memory buffer
the code could throw a "ReferenceError: _SDL_LockSurface is not defined"
if SDL_LockSurface was not used elsewhere in the C code.
optimize relooper id counters
Merge pull request #1954 from richq/lockref

Fix missing SDL_LockSurface reference
Define behavior that 'emcc -c a.c -o dir/' shall compile and generate object file 'dir/a.o'. Previous behavior when directory was specified in -o was accidental, and it generated an object file 'dir/a_0.o'. Add new command line option --default-obj-ext that allows specifying the file suffix that is used when the output object filename is generated in this manner. '.o' is a good default suffix since it parallels the existing gcc/clang/linux convention. For Windows Visual Studio+CMake+Emscripten integration, CMake has been hardcoded to assume that if Visual Studio is targeted, the compiler will always generate '.obj' files. Hence having the ability to adjust the default naming scheme with --default-obj-ext enables working around CMake inflexibility, and add support for CMake+VS+Emscripten triple.
Merge pull request #1928 from anlambert/webgl_ANGLE_instanced_arrays

Add support for WebGL hardware instancing through extension ANGLE_instanced_arrays
Merge pull request #1946 from juj/default_obj_ext

--default-obj-ext
Add support for generating vs-tool Visual Studio project files from CMake for building with Emscripten. This requires a custom build of CMake to work, since by default, CMake does not allow targeting other platforms than a few hardcoded ones ("win32", "x64", "itanium").
fix other.test_crunch
disable jcache in fastcomp, and fake emscripten_jcache_printf
fix --save-bc in fastcomp
disable some other.* tests in fastcomp
sanity check for js backend in fastcomp