Allow some makemon flags in lua monster creation

Also document the des.monster hash parameter values.

include/sp_lev.h

@@ -141,6 +141,7 @@ typedef struct {
         paralyzed, stunned, confused, waiting;
     long seentraps;
     short has_invent;
+    long mm_flags; /* makemon flags */
 } monster;
 
 typedef struct {