new macro 'luaM_reallocvchar' to allocate arrays of chars (avoids

uneeded tests and respective warnings)

lzio.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lzio.h,v 1.27 2013/06/07 14:51:10 roberto Exp roberto $
+** $Id: lzio.h,v 1.28 2014/01/31 15:14:22 roberto Exp roberto $
 ** Buffered streams
 ** See Copyright Notice in lua.h
 */
@@ -37,7 +37,8 @@ typedef struct Mbuffer {
 
 
 #define luaZ_resizebuffer(L, buff, size) \
-	(luaM_reallocvector(L, (buff)->buffer, (buff)->buffsize, size, char), \
+	((buff)->buffer = cast(char *, luaM_reallocvchar(L, (buff)->buffer, \
+						(buff)->buffsize, size)), \
 	(buff)->buffsize = size)
 
 #define luaZ_freebuffer(L, buff)	luaZ_resizebuffer(L, buff, 0)