Added total memory allocated counter to talloc, so we can tell if a talloc

Added total memory allocated counter to talloc, so we can tell if a talloc
pool is getting bloated. Also added a talloc_zero function to return zeroed memory.
Added debug in rpc_server/srv_pipe_hnd.c so we know when a talloc pool is being
freed. Syncup with srv_pipe_hnd.c from 2.2 so we are freeing memory at the same time.
Jeremy.
(This used to be commit d3a56c6042acf037bbd53de88d7636a5803ead20)