The configure scripts exits on a non zero exit code even with a warning. Even
though for upstream this is just a warning, for portage this means failure and 
it will exit.
We therefore alter the exit codes where neccesary.

--- a/configure.ac
+++ b/configure.ac
@@ -4588,7 +4588,6 @@ if test "$have_motif" = no -a "$have_gtk" = no; then
   else
     warnL "The GTK libraries do not seem to be available; the"
     warn2 "\`xscreensaver-settings' program requires them."
-    CONF_STATUS=1
 #   echo ''
 #   warn2 'You can use Motif or Lesstif instead of GTK (use the'
 #   warn2 "\`--with-motif' option) but that is NOT recommended."
@@ -4615,7 +4614,6 @@ if test "$have_gtk" = yes -a "$have_gdk_pixbuf" = no ; then
   warn  "GTK is being used, but the GDK-Pixbuf library and/or"
   warn2 "headers were not found.  That can't be good.  Please"
   warn2 "install the GDK-Pixbuf development kit and re-configure."
-  CONF_STATUS=1
 fi

 if test "$have_motif" = yes -a "$have_lesstif" = yes ; then
@@ -4733,7 +4731,6 @@ if test "$have_png" = no ; then

   if test "$png_halfassed" = yes ; then halfassery ; fi
   warn2 "Many things aren't going to work right."
-  CONF_STATUS=1
 fi