Detection of Parameter Direction in DeriveParameters method.

This detection is necessary because currently this method defaults all parameters with Input direction and when using functions that have OUT or INOUT parameters they aren't updated.
(PR - updated for current master)
DeriveParameters Test (updated)

Update the test to work properly with versions of PostgreSql before 9.x
PR Updated with Shay's changes.

See https://github.com/roji/Npgsql/commit/158eb05477a2acc32ca0a920a37af7c6997f727e
and https://github.com/roji/Npgsql/commit/abe8a04e86a12c4d16cb882e2c1049506633803e
PR Updated with Shay's changes.

See https://github.com/roji/Npgsql/commit/158eb05477a2acc32ca0a920a37af7c6997f727e
and https://github.com/roji/Npgsql/commit/abe8a04e86a12c4d16cb882e2c1049506633803e
Merge pull request #118 from NoeGarcia/master

Detection of Parameter Direction in DeriveParameters method.