[PATCH] pgsql async query functions

I really need async query functions for pgsql, so I wrote it. All functions are *simple* libpq wrapper. This patch is safe to apply. Async query can be very useful to improve performance, since pg_sendquery() returns immediately, then user can use pg_getresult() to get result later. (Especially when user have multiple db server) Missing feature is that raise warning or prohibit async query on persistent connection, since it can cause problems. I haven't implemented this, yet. Could anyone apply this patch? Thank you. -- Yasuo Ohgaki