- Add support for linearly desaturating images via r_greyscale

- Use correct luminance values for rendering textures
Patch submitted by Forrest Voight.

code/qcommon/q_shared.h

@@ -1307,4 +1307,7 @@ typedef enum _flag_status {
 #define CDCHKSUM_LEN 2
 
 
+#define LERP( a, b, w ) ( ( a ) * ( 1.0f - ( w ) ) + ( b ) * ( w ) )
+#define LUMA( red, green, blue ) ( 0.2126f * ( red ) + 0.7152f * ( green ) + 0.0722f * ( blue ) )
+
 #endif	// __Q_SHARED_H