Fix prot from shape changers at level generation

Mimics and other shape changers created at level generation
did not obey protection from shape changers.

src/makemon.c

@@ -1988,7 +1988,7 @@ register struct monst *mtmp;
     struct obj *otmp;
     int mx, my;
 
-    if (!mtmp)
+    if (!mtmp || Protection_from_shape_changers)
         return;
     mx = mtmp->mx;
     my = mtmp->my;

src/sp_lev.c

@@ -1585,7 +1585,8 @@ struct mkroom *croom;
          * eventually be expanded.
          */
         if (m->appear_as.str
-            && ((mtmp->data->mlet == S_MIMIC) || mtmp->cham)) {
+            && ((mtmp->data->mlet == S_MIMIC) || mtmp->cham)
+            && !Protection_from_shape_changers) {
             int i;
 
             switch (m->appear) {