Correct TRASH() macro usage

TRASH was mapped to TRASH_FREE and was supposed to be used for memory
that should not be accessed anymore, while TRASH_ALLOC() is to be
used for uninitialized but to-be-used memory.

But sometimes TRASH() was used in the latter sense.

Remove TRASH() macro, always use explicit TRASH_ALLOC() or TRASH_FREE().

sql/sql_cursor.cc

@@ -187,7 +187,7 @@ void Server_side_cursor::operator delete(void *ptr, size_t size)
   MEM_ROOT own_root= *cursor->mem_root;
 
   DBUG_ENTER("Server_side_cursor::operator delete");
-  TRASH(ptr, size);
+  TRASH_FREE(ptr, size);
   /*
     If this cursor has never been opened mem_root is empty. Otherwise
     mem_root points to the memory the cursor object was allocated in.