add mechanism to add a C library dependency from a JS library, in emcc
make sdl malloc hack nicer, and improve back deps trick
move deps info to file
TODO
test for eglGetProcAddress
move system libs calculation to its own file
add test for getProcAddress that requires we allow collisions in the main namespace with gl* functions
system libs fixes
move emscripten_GetProcAddress to a C library, so that it is less hackish and can work in fastcomp
add -O1 testing to browser.test_cubegeom_proc
Use -mllvm -disable-llvm-optzns.

The -O options affect the clang front-end in a variety of ways, so allow
them to be passed through to clang. To disable just the optimization passes,
use -mllvm -disable-llvm-optzns.