Make tests/test_html5_fullscreen.c standalone-compilable outside test suite.
Register mouse callbacks in test_html5_fullscreen.c sample so that it can be tested on IE as well.
Fix IE fullscreen requests to not run in mousedown events, since IE doesn't allow them. Related to #2219.
Fix typo with missing parentheses from previous commit that broke keyevents from performing deferred fullscreen/pointerlock requests.
Merge remote-tracking branch 'upstream/incoming' into incoming