Fix mistake in testing for null password; add contents with links to MaxAdmin reference guide.

server/modules/include/mysql_client_server_protocol.h

@@ -134,9 +134,6 @@ typedef struct mysql_session {
 #endif
 } MYSQL_session;
 
-/* The following can be compared using memcmp to detect a null password */
-uint8_t null_client_sha1[MYSQL_SCRAMBLE_LEN]="";
-
 /** Protocol packing macros. */
 #define gw_mysql_set_byte2(__buffer, __int) do { \
   (__buffer)[0]= (uint8_t)((__int) & 0xFF); \