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_cmds.c

@@ -203,11 +203,11 @@ void	R_AddCapShadowmapCmd( int map, int cubeSide ) {
 
 /*
 =============
-R_PostProcessingCmd
+R_AddPostProcessCmd
 
 =============
 */
-void	R_AddPostProcessCmd( ) {
+void	R_AddPostProcessCmd( void ) {
 	postProcessCommand_t	*cmd;
 
 	cmd = R_GetCommandBuffer( sizeof( *cmd ) );