Fix compiling of xscreensaver plugin

Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
(cherry picked from commit 9b2c6f22)

configure.ac

@@ -3334,7 +3334,7 @@ AS_IF([test "${enable_xcb}" != "no"], [
   dnl libxcb
   PKG_CHECK_MODULES(XCB, [xcb])
   PKG_CHECK_MODULES(XCB_SHM, [xcb-shm])
-  VLC_ADD_PLUGIN([screensaver xcb_x11 xcb_window xcb_screen xcb_apps])
+  VLC_ADD_PLUGIN([xscreensaver xcb_x11 xcb_window xcb_screen xcb_apps])
 
   AS_IF([test "${enable_xvideo}" != "no"], [
     PKG_CHECK_MODULES(XCB_XV, [xcb-xv >= 1.1.90.1], [