Log Message:
devel: Remove rx

This no longer has any users in pkgsrc and was discontinued upstream.

The GNU website says:

RX has been decommissioned, since no one has come forward to revive it, to \ 
improve it over the other free software regex library programs that are \ 
available, which would be quite a big task. (If you are interested after all, \ 
email <maintainers@gnu.org>

For a current regex implementation, we recommend using the regex code from \ 
Gnulib; see also the Regular expressions chapter in the Gnulib manual. (Also, if \ 
all you need is POSIX regexp functionality, any modern C library should provide \ 
that.)

The one-time regex standalone library has likewise been decommissioned in favor \ 
of the above.

(It's been unmaintained since at least 2010).