fix glCompressedTexSubImage2D; fixes #2173
Merge pull request #2174 from sunfishcode/incoming

Two minor testsuite cleanups.
add a test for fastcomp issue 24
Full screen fixes (aspect ratio & IE11) & AR opt

Full screen image now has correct aspect ratio (parent of canvas is full
screen root, canvas size is adapted via styles).
Full screen now works properly in Internet Explorer 11.
It is now possible to optionally force a specific aspect ratio for the
canvas (canvas size is adapted via styles, ratio for now has to be set
manually in compiled JS).
Merge branch 'incoming' of github.com:DerKoun/emscripten-fullscreen-improvements into incoming

Conflicts:
	AUTHORS
fix some whitespace
improve assertions message on function pointer errors
mention ASSERTIONS in abort() calls
extra testing for ASSERTIONS == 2
add test for #2175
fix other.test_dangerous_func_cast
sort function signatures in ASSERTIONS=2 abort message dumps, attempting to show most likely related ones first
add test for phi with unreachable source with a 64-bit value
mention that EMSCRIPTEN_KEEPALIVE also exports for you
fix ASSERTIONS output on bad function pointer calls
update other.test_emcc
put emscripten version in emscripten-version.txt, like other repos
add canvas.style.setProperty in headlessCanvas
Tidy up and fix several tests in tests/cases.
Eliminate undefined behavior in test_sscanf_other_whitespace.in.