Use of $_ produces warnings which can cause build failures in certain consumers.

Backported from revision 1.4 upstream (http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/pkg-config/OpenBSD/PkgConfig.pm).

Gentoo-bug: 538012
Gentoo-bug: 545314
Gentoo-bug: 545322
Gentoo-bug: 545962

--- a/src/usr.bin/pkg-config/OpenBSD/PkgConfig.pm
+++ b/src/usr.bin/pkg-config/OpenBSD/PkgConfig.pm
@@ -91,7 +91,6 @@
 {
 	my ($class, $fh, $name) = @_;
 	my $cfg = $class->new;
-	my $_;
 
 	$name = '' if !defined $name;
 	while (<$fh>) {