Include nspr cflags to prevent build failure
Inspired in yelp patch https://bugs.gentoo.org/295016

---

--- configure.ac.orig	2010-02-01 18:58:38.000000000 +0100
+++ configure.ac	2010-02-01 18:59:25.000000000 +0100
@@ -145,6 +145,7 @@
 		  gconf-2.0
 		  gnome-desktop-2.0 >= $GNOME_DESKTOP_REQUIRED
 		  libstartup-notification-1.0 >= $LIBSTARTUP_NOTIFICATION_REQUIRED
+		  nspr >= 4.7.4
 		  $LIBCANBERRA_GTK_PACKAGE
 		  $LIBNOTIFY_PACKAGE
 		  ])