API checks now have explanatory messages

lapi.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lapi.h,v 2.4 2009/03/10 17:14:37 roberto Exp roberto $
+** $Id: lapi.h,v 2.5 2009/04/03 15:58:03 roberto Exp roberto $
 ** Auxiliary functions from Lua API
 ** See Copyright Notice in lua.h
 */
@@ -11,7 +11,8 @@
 #include "llimits.h"
 #include "lstate.h"
 
-#define api_incr_top(L)   {L->top++; api_check(L, L->top <= L->ci->top);}
+#define api_incr_top(L)   {L->top++; api_check(L, L->top <= L->ci->top, \
+				"stack overflow");}
 
 #define adjustresults(L,nres) \
     { if ((nres) == LUA_MULTRET && L->ci->top < L->top) L->ci->top = L->top; }