Fixes basic water rendering on GLES (replaces GL_QUADS with GL_TRIANGLES).
Sets SDL2 to use correct profile for GLES.
Cleans up some old SDL 1.3 version checks.
Fixes fancy waves rendering on GLES (replaces GL_QUADS with GL_TRIANGLES)
Merge branch 'gles-testing' of https://github.com/historicbruno/0ad into gles-testing