Print correct program name when installed

Previously, the program-name calculation was broken when the program was
run from the path because it depended on a slash in argv[0]. This commit
defaults to the full argv[0] value in this case.
Update copyright and version
Add -b "begin at first match" option

For completeness, support outputting from the first match of the given
regular expression instead of the last. This is essentially the same as
    sed -n -e '/REGEX/,$p'
The -b option makes sense only in combination with -r, and is ignored
otherwise.
Add clean and uninstall targets to Makefile

These targets have the usual semantics: clean deletes the retail binary
and Makefile.conf, while uninstall removes $PREFIX/bin/retail.
Comment functions and tricky patches of code
Check for getline in configure

getline was standardised in POSIX-2008 and may now be on some non-GNU
systems, so the ifndef __GLIBC__ wrapping its implementation is
incorrect. This commit checks whether the function is defined during
configure instead.