Clean up portal mission code It's a mess!

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

Fully support emscripten toolchain in our build system

Import the Emscripted toolchain configuration

Hijack SDL2 and GLEW include and library when compiling to javascript emscripten already provides the SDL2 suite and will simply ignore missing libraries.

Work around how emscripten defines rwops

Work around emscripten not finding math.h

Add support for compiling C engine with emscripten