add support for ARB_texture_env_combine

stepmania/src/RageDisplay_OGL.cpp

@@ -1419,7 +1419,7 @@ void RageDisplay_OGL::SetTextureModeModulate()
 
 void RageDisplay_OGL::SetTextureModeGlow()
 {
-	if( !GLExt.m_bEXT_texture_env_combine )
+	if( !GLExt.m_bARB_texture_env_combine && !GLExt.m_bEXT_texture_env_combine )
 	{
 		/* This is changing blend state, instead of texture state, which isn't
 		 * great, but it's better than doing nothing. */

stepmania/src/RageDisplay_OGL_Extensions.cpp

@@ -82,6 +82,7 @@ void GLExt_t::Load( LowLevelWindow *pWind )
 
 	GetGLExtensions( g_glExts );
 
+	m_bARB_texture_env_combine = HasExtension("GL_ARB_texture_env_combine");
 	m_bEXT_texture_env_combine = HasExtension("GL_EXT_texture_env_combine");
 	m_bGL_EXT_bgra = HasExtension("GL_EXT_bgra");
 

stepmania/src/RageDisplay_OGL_Extensions.h

@@ -9,6 +9,7 @@ typedef bool (APIENTRY * PWSWAPINTERVALEXTPROC) (int interval);
 class LowLevelWindow;
 struct GLExt_t
 {
+	bool m_bARB_texture_env_combine;
 	bool m_bEXT_texture_env_combine;
 	bool m_bGL_EXT_bgra;