Fixes several issues in the current `man(1)` completion:
- _section_ numbers are not stripped off
- _Perl Programmers Reference Guide_ (`3p`) section is ignored
- manual page name can only be completed as the 1st argument
While there, add several more manual page hierarchies, i.e. `cat*`
for _graphiz_ on OpenBSD, `/usr/local/share/man` on macOS, etc.