perl: Guestfs.c file is not translatable, don't include it in po/POTFILES.

Reported by Nikos Skalkotos
https://aur.archlinux.org/packages/libguestfs/

Makefile.am

@@ -320,7 +320,7 @@ po/POTFILES: configure.ac
 	rm -f $@ $@-t
 	cd $(srcdir); \
 	find $(DIST_SUBDIRS) -name '*.c' -o -name '*.pl' -o -name '*.pm' | \
-	grep -v -E '^(examples|gnulib|gobject/docs|perl/(blib|examples)|po-docs|tests|test-data)/' | \
+	grep -v -E '^(examples|gnulib|gobject/docs|perl/(blib|examples)|perl/lib/Sys/Guestfs\.c|po-docs|tests|test-data)/' | \
 	grep -v -E '/((guestfs|rc)_protocol\.c)$$' | \
 	grep -v -E '^python/utils\.c$$' | \
 	LC_ALL=C sort > $@-t

po/POTFILES

@@ -337,7 +337,6 @@ p2v/ssh.c
 p2v/utils.c
 p2v/whole-file.c
 perl/bindtests.pl
-perl/lib/Sys/Guestfs.c
 perl/lib/Sys/Guestfs.pm
 php/extension/guestfs_php.c
 python/actions-0.c