add support for loading PVR images

this is from Q3A for Dreamcast

code/renderercommon/tr_common.h

@@ -146,6 +146,7 @@ void R_LoadBMP( const char *name, byte **pic, int *width, int *height );
 void R_LoadJPG( const char *name, byte **pic, int *width, int *height );
 void R_LoadPCX( const char *name, byte **pic, int *width, int *height );
 void R_LoadPNG( const char *name, byte **pic, int *width, int *height );
+void R_LoadPVR( const char *name, byte **pic, int *width, int *height );
 void R_LoadTGA( const char *name, byte **pic, int *width, int *height );
 
 /*