Silence "narrowing conversion" warning in Cygwin.
Silence "narrowing conversion" warning in Cygwin.

Fixes #151.

The compiler warned about a "narrowing conversion" from `unsigned int`
to `long`.  It's really more of a signedness warning.

jtv/libpqxx,jtv/libpqxx,jtv/libpqxx,jtv/libpqxx