Update shaders to conform to GLSL 1.3
-also added antialias shaders
Cleanup and new user-controls for gldemo

Cleanup:
 -removed SDL support
 -'terrain' scene is non-optional
 -removed local vector ops (vAdd, etc) in favor of existing glmatrix
New controls:
 -distort shader selection (keys 1,2,3,4)
 -simple movement (wasd, but s,d rotate body rather than strafe)
 -fullscreen toggle (TAB)
Lower backbuffer res from 1920 to 1600