Find tests in .oct files
Find tests in .oct files

"help meh.oct" doesn't work so strip the ".oct" if specified.  This
makes `doctest .` work.  If both meh.oct and meh.m are present,
"help meh" will get the .oct file; this does the same.  `doctest meh.m`
will explicitly test the .m file.  This may work for mex files although
I haven't tested that.

Fixes #178.

catch22/octave-doctest