Better memory management

[pszturmaj]

See

ddb/source/ddb/postgres.d

Line 1049 in f45f0ba

msg = new ubyte[len];

This was supposed to be temporary, until I'd finish other parts, but stayed here until now. It needs to be rewritten to reuse the buffer if possible. I would leave it as is for big messages, with configurable threshold in bytes and for messages smaller than threshold I would reuse a growable buffer. This change should prevent many unnecessary allocations and is fairly simple to do.

A little more complex but better solution would be receiving a fixed size buffer, then consuming that buffer field by field, and when you read past end of the buffer it should refresh the buffer with new content under the hood.