OpenGL2: Misc fixes and cleanup

Fix two constants in GLSL shaders. Remove f suffix from float and fix
int to float assignment. They were causing shader compile errors in
OpenGL ES 2 context.

Remove disabling clip plane. Clip plane is unused and never enabled in
the opengl2 renderer. Remove disabling it to avoid causing a GL error
when using OpenGL 3.2 core profile or OpenGL ES.

Make VAO cache vertex stride be size of srfVert_t since that is what
is uploaded to the GPU. No behavior change. There is a disabled debug
id in srfVert_t though which if enabled changes srfVert_t size.

code/renderergl2/tr_scene.c

@@ -435,7 +435,7 @@ void RE_BeginScene(const refdef_t *fd)
 }
 
 
-void RE_EndScene()
+void RE_EndScene(void)
 {
 	// the next scene rendered in this frame will tack on after this one
 	r_firstSceneDrawSurf = tr.refdef.numDrawSurfs;