Clean up strings, hats, flags and graves in Portal mission Mostly fixes poor grammar and spelling

merging Wuzzy's feedback fix

Fix bad layouting of feedback dialog, fixes #58

fix default binding for F10 / slot 10 not working

fix sounds not playing on first play (=load), because function bailed on success, rather than error. introduced in bd9a2f1b0080 , addressing issue #111

travis: Use correct vorbis flag in sdl2_mixer install Revert the addition of cmake which is already instealled.

Correctly set WEBGL macro during pas2c conversion

Disable stereo rendering when compiled with pas2c