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_glsl.c

@@ -331,17 +331,6 @@ static void GLSL_GetShaderHeader( GLenum shaderType, const GLchar *extra, char *
 								AGEN_LIGHTING_SPECULAR,
 								AGEN_PORTAL));
 
-	Q_strcat(dest, size,
-							 va("#ifndef texenv_t\n"
-								"#define texenv_t\n"
-								"#define TEXENV_MODULATE %i\n"
-								"#define TEXENV_ADD %i\n"
-								"#define TEXENV_REPLACE %i\n"
-								"#endif\n",
-								GL_MODULATE,
-								GL_ADD,
-								GL_REPLACE));
-
 	fbufWidthScale = 1.0f / ((float)glConfig.vidWidth);
 	fbufHeightScale = 1.0f / ((float)glConfig.vidHeight);
 	Q_strcat(dest, size,