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