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
Build from source section updates. New standalone docs for SDK. Clear messaging on which should be used where:
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
whitespace fix
fix doc for emscripten_push_**_main_loop
Merge pull request #2670 from coolwanglu/pr2

fix doc for emscripten_push_**_main_loop
add an optional node to FS.ErrnoError, and use it in stat to tell if an error is about the relevant file - if not, it occurred when looking up its parents, and we should emit ENOTDIR; fixes #2669
force llvm debug info in SAFE_HEAP>=2 in slowcomp
do not save debug info if js opts will remove it anyhow
qwe