Code reformat: split library names into separate lines

make git life a bit easy
Signal-related function implementations moved to separate file

When stubs are used, message will be printed using console.error()

alarm() and ualarm() throws exception now instead of stub. Using stubs
may significantly break applications.

siginterrupt() calls stub instead of exception. Since syscalls are never
interrupted in emscripten, it is better not to raise exception here.
changes to building from articles as a result of feedback from ChrisM. Significant fixes to LLVM-Backend doc
support coroutine

valid asm.js

better test case for coroutine

coding style

fix asm.js

fix test case

save STACK_MAX for coroutine

customized stack size for coroutine

move doc to new stie

fix typo
do not pass -g to LLVM if we were passed -gX with low X (less than 4, which is when we do include LLVM debug info); fixes #2657
allow websocket urls with slashes; fixes #2610
Merge branch 'master' of https://github.com/socketpair/emscripten into incoming

Conflicts:
	AUTHORS
verify file packager paths do not contain invalid characters; fixes #2649
add VoidPtr type to WebIDL binder, for void*
Build from source section updates. New standalone docs for SDK. Clear messaging on which should be used where:
fix test_unistd_misc
document 'any' type in webidl binder
some commented-out logging options
avoid copying bitcode files in emcc when possible; copy them lazily when actually required
clean up -g handling
test for repeated -gX params
add faq entry about using main() to know when it is safe to call compiled methods, after startup is all complete
Merge pull request #2661 from hamishwillee/incoming

Building from source site section updates
fix extra _ in docs; fixes #2659
Merge pull request #2612 from coolwanglu/coroutine

support coroutine