perl: fix license info

According to the README, perl can be used either under
Artistic or under GPLv1+ license, so include both.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/perl/perl.mk

@@ -8,8 +8,8 @@ PERL_VERSION_MAJOR = 18
 PERL_VERSION = 5.$(PERL_VERSION_MAJOR).1
 PERL_SITE = http://www.cpan.org/src/5.0
 PERL_SOURCE = perl-$(PERL_VERSION).tar.bz2
-PERL_LICENSE = Artistic
-PERL_LICENSE_FILES = Artistic
+PERL_LICENSE = Artistic or GPLv1+
+PERL_LICENSE_FILES = Artistic Copying README
 PERL_INSTALL_STAGING = YES
 
 PERL_CROSS_VERSION = 0.8