Feature to enable asynchronous event driven of network events
replace 111 error code literal with ERRNO_CODES.ECONNREFUSED as prompted by juj
Improve callback mechanism to allow an arbitrary userData pointer to be passed during callback registration that will subsequently be passed to the callback
Improve error handling on getsockopt when a level other than SOL_SOCKET or an optname other than SO_ERROR is supplied as per the conversation with juj
Make debug message for the default logging on error handler use Module.printErr rather than Module.print as suggested by juj
Add some more documentation to emscripten.h to explain that the JavaScript error callback takes an array containing the file descriptor, error code and error message.
Modify server on error to be consistent with the client on error
fix the build failures (we should only delete the jcache directory, not everything)
Add missing libc files to the build.
add tests for SDL_GetRGB and SDL_GetRGBA
clean up how PYTHON is specified.  it is not specified in .emscripten by default
Add a note to clarify requirements placed by DOM Level 3 spec on the browser resize event.
cherry-pick musl 1.1.3 wcsxfrm.c, fixes #2473
Merge pull request #2470 from sronsse/sdl

add tests for SDL_GetRGB and SDL_GetRGBA
Merge pull request #2469 from chadaustin/use-sys-executable

clean up how PYTHON is specified.  it is not specified in .emscripten by default
check return codes when building system libs
update musl from 0.9.13 to 1.0.3
update sanity.test_firstrun
fix sanity.test_emcc_caching
disable test_math_lgamma in non-fastcomp