Log Message:
Updated package to latest version, 1.7.3. Apart from a pkgsrc patch that
allows for installation of .cmxs files, changes include:

1.7.3:
Fix regarding num-top: this library is now also optional, as num.

1.7.2:
Trying to protect against failures when several package installs are done in
parallel.

New subpackage "findlib.top" for the toploop (Jeremie Dimino).

The "num" library is now optional.

Shell scripts are started via "sh" command when there is no /bin/sh (ygrek)