Allow executable being documented by exec2man.sh to be specified with
a relative path.
Output cogent usage instructions when invoked incorrectly.
Use politically correct $(...) as `...` has been deprecated by
glorious POSIX.
Allow allexec2man.sh to use relative paths to exec2man.sh
Pass appropriate options to txt2man to get a proper .TH line.
These are -s 1 for the section,
we skip -d xxx for the date, which will default to the
debian/changelog timestamp during a debian package build, or otherwise
to the current date.
Then -r origin-aka-project-name-and-version -v volume-aka-section-name.
Gbp-Pq: Name 0003-txt2man-options.patch
Omar Shrit