OpenGL2: Detect Intel graphics and avoid/use certain operations there.

Also use qglCopyTextureSubImage2DEXT instead of qglCopyTextureImage2DEXT.

code/renderergl2/tr_local.h

@@ -1373,6 +1373,8 @@ typedef struct {
 	int openglMajorVersion;
 	int openglMinorVersion;
 
+	qboolean    intelGraphics;
+
 	qboolean    drawRangeElements;
 	qboolean    multiDrawArrays;
 	qboolean	occlusionQuery;