Modified pipelined request function by splitting up the the provided queries

Modified pipelined request function by splitting up the the provided queries
in parts. Now we do a request for 32 queries and retrieve the response
before we continue with the next 32 queries.

The number 32 is experimental and should be tested on Exchange 2000 because
that was the imap-server which drops the connection with 100 calls at once.
Maybe we should lower it or raise it.

git-svn-id: https://svn.code.sf.net/p/squirrelmail/code/trunk/squirrelmail@5196 7612ce4b-ef26-0410-bec9-ea0150e637f0