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_dsa.c

@@ -35,7 +35,7 @@ static struct
 }
 glDsaState;
 
-void GL_BindNullTextures()
+void GL_BindNullTextures(void)
 {
 	int i;
 
@@ -141,7 +141,7 @@ GLvoid APIENTRY GLDSA_GenerateTextureMipmapEXT(GLuint texture, GLenum target)
 	qglGenerateMipmap(target);
 }
 
-void GL_BindNullProgram()
+void GL_BindNullProgram(void)
 {
 	qglUseProgram(0);
 	glDsaState.program = 0;
@@ -205,7 +205,7 @@ GLvoid APIENTRY GLDSA_ProgramUniformMatrix4fvEXT(GLuint program, GLint location,
 	qglUniformMatrix4fv(location, count, transpose, value);
 }
 
-void GL_BindNullFramebuffers()
+void GL_BindNullFramebuffers(void)
 {
 	qglBindFramebuffer(GL_FRAMEBUFFER, 0);
 	glDsaState.drawFramebuffer = glDsaState.readFramebuffer = 0;