Fix Gentoo builds of Perl-y bits
Fix Gentoo builds of Perl-y bits

Josef 'Jeff' Sipek reports that Gentoo does not procude .packlist files
when building perl modules. In order to keep Gentoo happy don't assume that
we're going to find such files and only try editing them if they exists.

Whoever decided to take on Gentoo packaging will have to figure out
a way of harvesting the file list.

adfernandes/pcp,wuliming/pcp,edwardt/pcp,aeg-aeg/pcpfans,adfernandes/pcp,mbaldessari/pcp,edwardt/pcp,tjanez/pcp,wuliming/pcp,aeg-aeg/pcpfans,andyvand/cygpcpfans,ryandoyle/pcp_original,wuliming/pcp,adfernandes/pcp,andyvand/cygpcpfans,aeg-aeg/pcpfans,wuliming/pcp,tjanez/pcp,prasincs/pcp,aeg-aeg/pcpfans,wuliming/pcp,edwardt/pcp,ryandoyle/pcp_original,wuliming/pcp,edwardt/pcp,ryandoyle/pcp_original,prasincs/pcp,aeg-aeg/pcpfans,mbaldessari/pcp,edwardt/pcp,tjanez/pcp,andyvand/cygpcpfans,ryandoyle/pcp_original,mbaldessari/pcp,mbaldessari/pcp,edwardt/pcp,ryandoyle/pcp_original,tjanez/pcp,prasincs/pcp,aeg-aeg/pcpfans,aeg-aeg/pcpfans,prasincs/pcp,ryandoyle/pcp_original,adfernandes/pcp,prasincs/pcp,tjanez/pcp,tjanez/pcp,adfernandes/pcp,prasincs/pcp,andyvand/cygpcpfans,mbaldessari/pcp,adfernandes/pcp,ryandoyle/pcp_original,mbaldessari/pcp,ryandoyle/pcp_original,wuliming/pcp,andyvand/cygpcpfans,andyvand/cygpcpfans,prasincs/pcp,edwardt/pcp,tjanez/pcp,adfernandes/pcp,edwardt/pcp,tjanez/pcp,wuliming/pcp,andyvand/cygpcpfans,andyvand/cygpcpfans,prasincs/pcp,adfernandes/pcp,aeg-aeg/pcpfans