Link to X11 libs.

Makefile.am

@@ -47,7 +47,9 @@ lib_libscreenshooter_la_LIBADD = \
 	@LIBXFCE4UTIL_LIBS@ \
 	@LIBXFCE4UI_LIBS@ \
   @GLIB_LIBS@ \
-	@SOUP_LIBS@
+	@SOUP_LIBS@ \
+	@LIBXEXT_LIBS@ \
+	@LIBX11_LIBS@
 
 lib_libscreenshooter_built_sources = \
 	lib/screenshooter-marshal.c lib/screenshooter-marshal.h

configure.ac.in

@@ -54,6 +54,8 @@ XDT_CHECK_PACKAGE([GTK], [gtk+-2.0], [2.16.0])
 XDT_CHECK_PACKAGE([GLIB], [glib-2.0], [2.16.0])
 XDT_CHECK_PACKAGE([SOUP], [libsoup-2.4], [2.26.0])
 XDT_CHECK_PACKAGE([EXO], [exo-1], [0.5.0])
+XDT_CHECK_PACKAGE([LIBXEXT], [xext], [1.0.0])
+XDT_CHECK_LIBX11()
 
 dnl **************************
 dnl *** Check for xsltproc ***