add mongo auth support, and copy a md5 lib to 3rd

3rd/lua-md5/compat-5.2.h

@@ -0,0 +1,15 @@
+#if !defined LUA_VERSION_NUM
+/* Lua 5.0 */
+#define luaL_Reg luaL_reg
+
+#define luaL_addchar(B,c) \
+  ((void)((B)->p < ((B)->buffer+LUAL_BUFFERSIZE) || luaL_prepbuffer(B)), \
+   (*(B)->p++ = (char)(c)))
+#endif
+
+#if LUA_VERSION_NUM==501
+/* Lua 5.1 */
+#define lua_rawlen lua_objlen
+#endif
+
+void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup);