Add install hook to replace xflock4

hooks/ebuild_install_post/xflock4.bash

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+source "${PALUDIS_EBUILD_DIR}/echo_functions.bash"
+
+if [[ "${CATEGORY}/${PN}" == "xfce-base/xfce4-session" ]] ; then
+	elog "Replacing /usr/$(exhost --target)/bin/xflock4!"
+
+	cat << EOF > "${IMAGE}"/usr/$(exhost --target)/bin/xflock4
+#!/bin/sh
+
+PATH=/bin:/usr/bin
+export PATH
+
+# else run another access locking utility, if installed
+for lock_cmd in \
+  "i3lock -c 000000"
+  do
+    set -- \$lock_cmd
+    if command -v -- \$1 >/dev/null 2>&1; then
+        \$lock_cmd >/dev/null 2>&1 &
+	# turn off display backlight:
+	xset dpms force off
+        exit
+    fi
+done
+
+# else access locking failed
+exit 1
+EOF
+
+fi