curses: change from malloc() to nethack's alloc()

There was no provision for malloc() potentially returning Null and it
wasn't integrated with nethack's MONITOR_HEAP.  'heaputil' shows that
the curses interface is leaking like a sieve.  If some things are
actually being allocated separately and then freed from within curses,
those need to be thoroughly documented and maybe switched back to
malloc().

win/curses/cursdial.c

@@ -478,7 +478,7 @@ curses_create_nhmenu(winid wid)
         return;
     }
 
-    new_menu = malloc(sizeof (nhmenu));
+    new_menu = (nhmenu *) alloc((signed) sizeof (nhmenu));
     new_menu->wid = wid;
     new_menu->prompt = NULL;
     new_menu->entries = NULL;
@@ -524,7 +524,7 @@ curses_add_nhmenu_item(winid wid, int glyph, const ANY_P * identifier,
 
     new_str = curses_copy_of(str);
     curses_rtrim((char *) new_str);
-    new_item = malloc(sizeof (nhmenu_item));
+    new_item = (nhmenu_item *) alloc((unsigned) sizeof (nhmenu_item));
     new_item->wid = wid;
     new_item->glyph = glyph;
     new_item->identifier = *identifier;
@@ -630,7 +630,8 @@ curses_display_nhmenu(winid wid, int how, MENU_ITEM_P ** _selected)
     curses_destroy_win(win);
 
     if (num_chosen > 0) {
-        selected = (MENU_ITEM_P *) malloc(num_chosen * sizeof (MENU_ITEM_P));
+        selected = (MENU_ITEM_P *) alloc((unsigned)
+                                         (num_chosen * sizeof (MENU_ITEM_P)));
         count = 0;
 
         menu_item_ptr = current_menu->entries;