#25 Bug fixes from NetBSD Pkgsrc

[David Sainty]

Some patches from NetBSD Pkgsrc:

Defining _XOPEN_SOURCE breaks the build under NetBSD.

The default C++ precision of 6 digits is Very risky in a database context.

As with DATE fields, if a TIME field is unset (hour value 24+), output an empty string.

Correctly terminate default string values on NUL.

[David Sainty]