engine: remove misplaced MAY_ALIAS

source/build/include/clip.h

@@ -65,7 +65,7 @@ extern void engineInitClipMaps();
 extern void engineSetClipMap(mapinfo_t *bak, mapinfo_t *newmap);
 
 #endif // HAVE_CLIPSHAPE_FEATURE
-typedef struct MAY_ALIAS
+typedef struct
 {
     union { struct { int32_t x1, y1; }; vec2_t p1; };
     union { struct { int32_t x2, y2; }; vec2_t p2; };