Support the "escape" bytea format when receiving data

This allows pq to operate correctly in both output formats, which
should help users who are still on PG 9.0 or have resorted to
setting bytea_output to "escape" for other reasons.

Even after this commit, bytea data is always sent in the "hex"
format.  This is not a problem for PostgreSQL versions 9.0 and later
as they are guaranteed to accept either format.  Older versions will
continue to experience problems, but it's not clear whether that
problem is worth fixing or not.
Merge pull request #195 from johto/bytea_escape

Support bytea_output=escape when receiving data
Add test for issue #196
Improved precision encoding support for float32 and float64

This ensures that all IEEE754 single and double precision floating
point values retain their full fidelity when submitted as parameters.
Add Matt Newberry to Contributors