branches/zip: fix a compiler error and a warning

Both are minor changes:
1) Compiler error introduced in r4072: double ';' at the end.
2) Warning introduced in r3613: \mem\mem0pool.c(481) : 
warning C4098: 'mem_area_free' : 'void' function returning a value

Approved by: Sunny (IM)

buf/buf0buf.c

@@ -1016,7 +1016,7 @@ buf_pool_drop_hash_index(void)
 	ut_ad(!btr_search_enabled);
 
 	do {
-		buf_chunk_t*	chunks	= buf_pool->chunks;;
+		buf_chunk_t*	chunks	= buf_pool->chunks;
 		buf_chunk_t*	chunk	= chunks + buf_pool->n_chunks;
 
 		released_search_latch = FALSE;

mem/mem0pool.c

@@ -478,7 +478,9 @@ mem_area_free(
 	ulint		n;
 
 	if (srv_use_sys_malloc) {
-		return(free(ptr));
+		ut_free(ptr);
+
+		return;
 	}
 
 	/* It may be that the area was really allocated from the OS with