New connection pool comment

[John Huss]

I'm working on integrating my apps with the latest changes and I noticed
that in the new connection pool there isn't a special exception thrown when
the pool is exhausted (too busy).  It was handy to be able to identify that
situation.

It's in UnmanagedPoolingDataSource line 326:
throw new SQLException("Can't obtain connection. Request to pool timed out.
Total pool size: " + pool.size());

It used to throw ConnectionUnavailableException

Any chance this can be reintroduced?

John