Change VCS tag to match specified format

The tag should start with type: of versioning type, followed by the url.
Therefore it cannot be used in source URLs directly.

Introduce %forgeurl variable with URL only. Use it in VCS tag and in
sources too. Thanks to Petr Pisar for documentation check.

whois.spec

@@ -5,15 +5,17 @@
 # Add libidn support
 %{bcond_with    whois_enables_idn}
 
+%global forgeurl https://github.com/rfc1036/whois
+
 Name:       whois       
 Version:    5.5.15
 Release:    1%{?dist}
 Summary:    Improved WHOIS client
 License:    GPLv2+
 URL:        https://www.linux.it/~md/software/
-VCS:        https://github.com/rfc1036/whois
+VCS:        git:%{forgeurl}
 # Source0:    http://ftp.debian.org/debian/pool/main/w/%%{name}/%%{name}_%%{version}.tar.xz
-Source0:    %{VCS}/archive/v%{version}/%{name}-%{version}.tar.gz
+Source0:    %{forgeurl}/archive/v%{version}/%{name}-%{version}.tar.gz
 BuildRequires:  coreutils
 BuildRequires:  gcc
 BuildRequires:  gettext