Firebird: Improved remote protocol

Dmitry Yemanov reports:

The remote protocol has been slightly improved to perform better in slow networks. In order to achieve this, more advanced packets batching is now performed, also there are some buffer transmission optimizations. In a real world test scenario, these changes showed about 50% less API roundtrips, thus causing about 40% less TCP roundtrips. Hopefully, this is an improvement some our users could benefit from (mostly it should affect over-the-internet database access).

This work has been committed into the HEAD branch to be included into the next Firebird version. Further protocol improvements are also planned.