Add groff as a BuildRequires to spec file

According to Fedora packaging guidelines, groff is not on the list
of package exceptions for BuildRequires.  A recent change in the Fedora
build system has triggered breakage in building rpm packages and it
is likely this package won't build for Fedora 18.

Reference:
http://fedoraproject.org/wiki/Packaging:Guidelines#Exceptions_2

Signed-off-by: Steven Dake <sdake@redhat.com>
Reviewed-by: Fabio Di Nitto <fdinitto@redhat.com>

corosync.spec.in

@@ -35,6 +35,7 @@ Conflicts: openais <= 0.89, openais-devel <= 0.89
 %define buildtrunk 0
 %{?_with_buildtrunk: %define buildtrunk 1}
 
+BuildRequires: groff
 BuildRequires: libqb-devel
 BuildRequires: nss-devel
 %if %{buildtrunk}