Update perl requires filtering

Switch to using the %perl_default_filter macro for filtering the perl
dependency. The older attempt which used a %__perl_requires override no
longer works on F19.

Some of the examples installed with %doc use perl, but we don't want the
whole openvpn package to start depend on perl because of that.

openvpn.spec

@@ -5,7 +5,7 @@
 
 Name:              openvpn
 Version:           2.3.1
-Release:           1%{?prerelease:.%{prerelease}}%{?dist}
+Release:           2%{?prerelease:.%{prerelease}}%{?dist}
 Summary:           A full-featured SSL VPN solution
 URL:               http://openvpn.net/
 #Source0:           http://openvpn.net/beta/%{name}-%{version}%{?prerelease:_%{prerelease}}.tar.gz
@@ -31,6 +31,8 @@ Group:             Applications/Internet
 BuildRequires:     lzo-devel
 BuildRequires:     openssl-devel
 BuildRequires:     pam-devel
+# For the perl_default_filter macro
+BuildRequires:     perl-macros
 BuildRequires:     pkcs11-helper-devel
 BuildRequires:     systemd-units
 # For /sbin/ip.
@@ -45,7 +47,7 @@ Requires(postun):  systemd-units
 
 # Filter out the perl(Authen::PAM) dependency.
 # No perl dependency is really needed at all.
-%define __perl_requires sh -c 'cat > /dev/null'
+%{?perl_default_filter}
 
 %description
 OpenVPN is a robust and highly flexible tunneling application that uses all
@@ -200,6 +202,9 @@ fi
 %exclude %{_datadir}/doc/%{name}/
 
 %changelog
+* Mon Apr 08 2013 Kalev Lember <kalevlember@gmail.com> 2.3.1-2
+- Update perl requires filtering
+
 * Tue Apr 02 2013 Jon Ciesla <limburgher@gmail.com> 2.3.1-1
 - 2.3.1, BZ 929402.