Add light type defined to gbi.h

gbi.h

@@ -1186,6 +1186,15 @@ typedef union {
     long long int force_structure_alignment[2];
 } Vp;
 
+/**
+  * Lighting types.
+  * LIGHT_TYPE_DIR: Standard directional light. Equivalent to 0.
+  * LIGHT_TYPE_POINT(x): Enables point lighting, with x acting as the kc coefficient.
+  */
+
+#define LIGHT_TYPE_DIR 0
+#define LIGHT_TYPE_POINT(x) x
+
 /**
  * Light structure.
  *