Merge pull request #2345 from lovasoa/fast-cwrap

Fast cwrap
fuzz larger testcases in relooper fuzzer
Merge branch 'archive_groups' of github.com:rsturgell/emscripten into incoming

Conflicts:
	AUTHORS
Migrate is*, to* and stro* to use musl libc.
Merge pull request #2369 from juj/musl_charfuncs

Musl charfuncs
1.18.3
wipe out emscripten.py output when it fails, so the error does not cascade weirdly; fixes #2368
Fix test breakages in s_* suites after musl_charfuncs merge.
Don't allow exceptions in SDL audio backend with Web Audio to leak and abort rAF loops.
Add a hack to SDL audio backend that lets user code to control which audio files are played back with <audio> element and which are played back with Web Audio.
write a bunch of unit tests for the desired javascript inheritance api
and of course, instanceof should work as you expect
sketch extend method
can extend, construct, and delete
instanceof passes
properties set in constructor persist to methods
A bunch of other tests pass now too.
concrete methods are accessible externally.  also rethink some other tests.
make optional methods work
pass jshint