removing the background pixel eliminates flicker when slimlock starts.

This makes for really nice transitions on window managers
such as awesome, or when the desktop background is the same as slimlocks
background.

slimlock.cpp

@@ -150,7 +150,6 @@ int main(int argc, char **argv) {
 
 	XSetWindowAttributes wa;
 	wa.override_redirect = 1;
-	wa.background_pixel = BlackPixel(dpy, scr);
 
 	// Create a full screen window
 	root = RootWindow(dpy, scr);
@@ -164,7 +163,7 @@ int main(int argc, char **argv) {
 	  DefaultDepth(dpy, scr),
 	  CopyFromParent,
 	  DefaultVisual(dpy, scr),
-	  CWOverrideRedirect | CWBackPixel,
+	  CWOverrideRedirect,
 	  &wa);
 	XMapWindow(dpy, win);