allocation function is not exactly API (and cannot raise errors

like other API functions); better not use 'api_check' for cheking it.

lmem.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lmem.c,v 1.89 2014/11/02 19:33:33 roberto Exp roberto $
+** $Id: lmem.c,v 1.90 2015/03/03 18:18:29 roberto Exp roberto $
 ** Interface to Memory Manager
 ** See Copyright Notice in lua.h
 */
@@ -85,8 +85,7 @@ void *luaM_realloc_ (lua_State *L, void *block, size_t osize, size_t nsize) {
 #endif
   newblock = (*g->frealloc)(g->ud, block, osize, nsize);
   if (newblock == NULL && nsize > 0) {
-    api_check( nsize > realosize,
-                 "realloc cannot fail when shrinking a block");
+    lua_assert(nsize > realosize);  /* cannot fail when shrinking a block */
     if (g->version) {  /* is state fully built? */
       luaC_fullgc(L, 1);  /* try to free some memory... */
       newblock = (*g->frealloc)(g->ud, block, osize, nsize);  /* try again */