add malloc related definition to rt_malloc.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@89 bbd45198-f89e-11dd-88c7-29a3b14d5316

libc/minilibc/stdlib.h

@@ -19,4 +19,9 @@
 int atoi(const char *nptr);
 #endif
 
+#define malloc  rt_malloc
+#define free    rt_free
+#define realloc rt_realloc
+#define calloc  rt_calloc
+
 #endif