Introduce a build-condition on groff

This allows to build perl without need of groff. The macro
_without_perl_enables_groff has "perl" identifier to compete with
perl.spec because this is a core module.

perl-Pod-Perldoc.spec

@@ -1,9 +1,13 @@
+# Optional features
+# Tk support
 %bcond_without tk
+# Support for groff
+%bcond_without perl_enables_groff
 
 Name:           perl-Pod-Perldoc
 # let's overwrite the module from perl.srpm
 Version:        3.28
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        Look up Perl documentation in Pod format
 License:        GPL+ or Artistic
 Group:          Development/Libraries
@@ -18,8 +22,10 @@ BuildRequires:  perl(ExtUtils::MakeMaker)
 BuildRequires:  perl(strict)
 BuildRequires:  perl(warnings)
 # Run-time:
+%if %{with perl_enables_groff}
 # Pod::Perldoc::ToMan executes roff
 BuildRequires:  groff-base
+%endif
 BuildRequires:  perl(Carp)
 BuildRequires:  perl(Config)
 BuildRequires:  perl(Encode)
@@ -56,8 +62,10 @@ BuildRequires:  perl(Tk::Pod)
 %endif
 %endif
 %endif
+%if %{with perl_enables_groff}
 # Pod::Perldoc::ToMan executes roff
 Requires:       groff-base
+%endif
 Requires:       perl(:MODULE_COMPAT_%(eval "`perl -V:version`"; echo $version))
 Requires:       perl(File::Temp) >= 0.22
 Requires:       perl(HTTP::Tiny)
@@ -104,6 +112,9 @@ make test
 %{_mandir}/man3/*
 
 %changelog
+* Mon Apr 03 2017 Petr Pisar <ppisar@redhat.com> - 3.28-2
+- Introduce a build-condition on groff
+
 * Thu Mar 16 2017 Petr Pisar <ppisar@redhat.com> - 3.28-1
 - 3.28 bump