This commit introduces support for special %PPID value that
can be passed to the -o option as a substitution for parent
PID. It also allows users to use two additional separators
for omitted PIDs - colon and semicolon.
As the sysvinit becomes obsolete, some of the bundled tools
need to find a new home. The procps-ng project seems to be
the most suitable project for adopting the pidof tool.
This commit introduces a redesigned version of pidof
that satisfies the LSB requirements.
In corner cases the behaviour might differ from the former
one as the new version doesn't use any stat(2) calls.
