...on NetBSD and FreeBSD and OpenBSD.

No actual logic change.

The -Winline option produce two warnings that are (probably correctly)
indicating that inlining normalize_tspec() and dtolfp() is inefficient.
I judge that it's not worth the hassle of reorganizing the code to fix
these, so we'll just tell the compiler to stifle.

Instead of sweeping inconveniennt truths under the rug, put them
in the closet.  On my list to get fixed.

-Winline now only with --enable-debug-warnings

Previous bugfix neglected to remove the column from the header.

IfstatsSummary.summary() now properly handles missing values, previous
version pretended to, but would have failed anyway.