Engine update and various improvements
RS3 plugin library:
- Added functions swapbuffers:readpixels and swapbuffers:copytosurface - see docs for more info
- createsurfacefrompng failure is now non-fatal, returning null if the image doesn't exist
- Fixed return type of scroll_direction (documented as boolean, but was returning an integer)
- Fixed alpha channels of surface:drawtosurface not behaving as expected
- Fixed plugin overlay being drawn above plugin windows and embedded browsers
- Fixed a minor issue with SDL-level hook signatures which might have caused a crash (but didn't actually seem to)
Launcher:
- Fixed launcher crash if custom launch command was invalid (i.e. exec() failure)
- PSAs (those official blue messages that appear above the 'play' button) will now never be cached, as the cached message was often being shown incorrectly
- Added SDL_VIDEODRIVER=x11 to the environment when launching RS3, as this is necessary to prevent it from crashing when using KDE 6.4 or newer, see #137
- Made startup much faster for people logged into more than one account
- Added a setting to disable automatically discarding invalid login sessions, see #118
- Added tooltips to general settings menu