update memory growth code, and ensure replace_memory is on the top in fastcomp
Update libcxx.
Provide a value for ELAST.
Bump emscripten version.
fix for empty file bug in idbfs
Merge pull request #2844 from waywardmonkeys/update-libcxx

Update libcxx
Remove redundant comment in src/library_gl.js for roundedToNextMultipleOf() which deals with positive size values.
added implementation of utimes (with an 's') like the existing utime
fix utimes to look at modtime ([1]) instead of atime ([0])
adding myself to AUTHORS file
Merge pull request #2845 from pkholland/incoming

fix for empty file bug in idbfs
Update ChangeLog to latest.
Force WebGL2.