Fixes for older server versions

Correct array element escaping for all versions (tested >= 8.0).
Execute server version dependant tests selectively.
Added test for escape formatted bytea data.
Added test for 'true'::boolean.
More test selectivity; all tests pass on 8.3 and up.
Moved some code out of a loop that doesn't need to execute on each iteration.
Merge pull request #70 from glenebob/bugs_8_4

Fixes for older server versions

Here are fixes for the array problem you found on 8.4, plus some changes to tests to make them run properly on more various versions.

I tested Npgsql on every final version of 8.0, 8.1, 8.2, 8.3, 8.4, 9.0, 9.1, 9.2, and 9.3 :)

-Glen