Started work on #1554
Added a script to extract struct sizes and field offsets as well as constant (#define) values.
Integrate the new tool into emscripten
Automatically compile struct_info.json and save the compiled version in the emscripten cache.
Updated library_sdl.js
Remove "-U__GNUC__" flag to avoid incorrect measurements.
Add timeb.h to struct_info.json
Replace references to QUANTUM_SIZE with C_STRUCTS equivalents.
Fix some comments and bump EMSCRIPTEN_VERSION
Merge branch 'incoming' of github.com:ngld/emscripten into incoming

Conflicts:
	AUTHORS
	src/library_sdl.js
	tools/shared.py
fix sanity.test_emcc_caching (we now have a cache dir earlier on)
update test_outline
fix other.test_static_link
run test_fs_nodefs_rw only in node
update unistd tests to run only on node