xsecurelock: Added missing X11 buildInputs

According to xsecurelock's configure.ac file, each of the add
dependencies are used to:

- libXrandr: XRandR provides information about monitor layouts and is
strongly recommended on systems which can use more than one monitor
(which includes most laptops).
- libXext: The X Synchronization extension is used to get per-device idle
times. Used by until_nonidle only.
- libXScrnSaver: The X11 Screen Saver extension is used to turn off the
screen saver when X11 handles screen blanking (e.g. via timeout) anyway.
Saves CPU power.

Adding libXrandr fixes an issue where locking a screen in a multi
monitor setup results in the prompt information to not be in the middle
of the screen. The other dependencies are not tested if they fixed
something, however since upstream recommends than I think it is fair to
include them also.

pkgs/tools/X11/xsecurelock/default.nix

@@ -1,6 +1,6 @@
 { lib, stdenv, fetchFromGitHub, autoreconfHook, pkgconfig
-, libX11, libXcomposite, libXft, libXmu, pam, apacheHttpd, imagemagick
+, libX11, libXcomposite, libXft, libXmu, libXrandr, libXext, libXScrnSaver
-, pamtester, xscreensaver, xset }:
+, pam, apacheHttpd, imagemagick, pamtester, xscreensaver, xset }:
 
 stdenv.mkDerivation rec {
   name = "xsecurelock-${version}";
@@ -17,8 +17,8 @@ stdenv.mkDerivation rec {
     autoreconfHook pkgconfig
   ];
   buildInputs = [
-    libX11 libXcomposite libXft libXmu pam
+    libX11 libXcomposite libXft libXmu libXrandr libXext libXScrnSaver
-    apacheHttpd imagemagick pamtester
+    pam apacheHttpd imagemagick pamtester
   ];
 
   configureFlags = [