statement caching patch from Laszlo Hornyak for review

[Dave Cramer <pg(at)fastcrypt(dot)com>]

Laszlo Hornyak has finished off the proof of concept patch that I  
submitted a few months ago.

This driver implements prepared statement caching and was used by Sun  
to achieve the excellent results for their benchmark.

Statement caching has proven to provide a 30-40% improvement in the  
benchmark results.

Because the files are quite large I've placed the patch at http:// 
beaver.fastcrypt.com/~davec/cachable.tar.gz

Currently it does not compile under 1.6, but works fine under 1.5.

Dave