Add the libpq use parameter to the dtc connection string.
Improve regression test for reading a bytea column to SQL_C_CHAR.

When converting a bytea to SQL_C_CHAR, the driver uses upper-case letters in
the hex output, while the backend uses lower-case letters. That leads to
different output when using bytea_output=hex than with bytea_output=escape.
Set bytea_output explicitly in the regression test, so that it works
regardless of the current bytea_output setting. And test both settings - the
code path taken in the driver is quite different.
Fix SQLTables column names to be ODBC version 3 compliant

In ODBC3, TABLE_QUALIFIER was renamed to TABLE_CAT, and TABLE_OWNER to
TABLE_SCHEM.

David Hedberg
Silence compilers warnings without _HANDLE_ENLIST_IN_DTC_ or USE_LIBPQ.

Compiler complained about unused variable.
Cleanup the code for *test* button and add the functionality to test
MSDTC support.