Optimize escapeStringConn

Not entirely sure why,  but the old binding exhibited non-linear slowdowns.
I'm guessing due to some kind of memory management behavior,  and may be
a performance problem inside GHC itself.  This may well be worth further
investigation.

I fixed the problem by mimicking bos's implementation of
Database.MySQL.Base.escape,  changing the binding to use
createAndTrim instead of mallocBytes/reallocBytes
Bump version to 0.8.2.3