use consistent unit suffixes. (#1353)

use consistent unit suffixes. (#1353)

* use consistent unit suffixes.

This is a user visible change. The suffixes for the distance
option of the arcdist, interpolate, radius and position filters
and the add option of the height filter are different.

* drop unused includes

* whitespace

* terminate fatal messages.

* change simplify to process distances in meters.

This simplifies option value parsing.
There is no user visible difference.

* define MYNAME in cc not h.