Automatically pick the correct X.org patch

Update RPM package build process to automatically detect and apply
the correct X.org patch.

contrib/packages/rpm/el7/SPECS/tigervnc.spec

@@ -1,6 +1,6 @@
 Name:           tigervnc
 Version:        @VERSION@
-Release:        4%{?snap:.%{snap}}%{?dist}
+Release:        5%{?snap:.%{snap}}%{?dist}
 Summary:        A TigerVNC remote display system
 
 Group:          User Interface/Desktops
@@ -137,7 +137,8 @@ pushd unix/xserver
 for all in `find . -type f -perm -001`; do
         chmod -x "$all"
 done
-patch -p1 -b --suffix .vnc < ../xserver120.patch
+xserver_patch="../xserver$(rpm -q --qf '%{VERSION}' xorg-x11-server-source | awk -F. '{ print $1 $2 }').patch"
+patch -p1 -b --suffix .vnc < "$xserver_patch"
 popd
 
 %build
@@ -296,6 +297,9 @@ fi
 %{_datadir}/selinux/packages/vncsession.pp
 
 %changelog
+* Mon Feb 11 2019 Mark Mielke <mmielke@ciena.com> 1.9.80-5
+- Automatically detect and apply the correct X.org patch.
+
 * Mon Jan 14 2019 Pierre Ossman <ossman@cendio.se> 1.9.80-4
 - Use system FLTK for build
 - Add libXrandr-devel as a dependency so x0vncserver gets resize support.