pcp

packaging changes - gentoo and perl

Add case for target_distro=gentoo in configure.in.

Change the Perl packaging logic for the non-Debian-like builds.

The generation of the .packlist files in the Perl builds does not
happen on all platforms when Makefile is generated from Makefile.PL
with ExtUtils::MakeMaker and INSTALLDIRS=vendor, so changed the
logic to use the "Installing ..."  lines from "make -f Makefile
install" to build the $(TOPDIR)/perl-pcp-*.list files (this is all
in the $PERL_GET_FILELIST macro defined in builddefs).  And if the
perl-pcp-*.list files are created, then use these to drive the PCP
packaging (the last step used to be only for the "darwin" platform,
but is needed for other platforms like Gentoo where the "packaging"
is simply a tarball).