1. taos_consume block for evev
2. taos_fetch_block returns 0 in subscription

prepare all subqueries object before launch subqueries. and add some check for global status object  during super table query.

fix the invalid release operations when the database is dropped and the metermeta cache is cleaned up at the client side. #1053  [tbase-1435]

add the null-terminated char for the binary data, if the space if available.