game: make gitem_t operations const

Author: 0lvin

src/g_ai.c

@@ -309,7 +309,7 @@ range(edict_t *self, edict_t *other)
  * to self, even if not infront()
  */
 qboolean
-visible(edict_t *self, edict_t *other)
+visible(const edict_t *self, const edict_t *other)
 {
 	vec3_t spot1;
 	vec3_t spot2;
@@ -684,7 +684,7 @@ FindTarget(edict_t *self)
 /* ============================================================================= */
 
 qboolean
-FacingIdeal(edict_t *self)
+FacingIdeal(const edict_t *self)
 {
 	float delta;