Revert "Add a configuration option for fullscreen locking"

now all fullcreen clients are rendered above tiled and floating clients

This partially reverts commit 326eee1444.

config.def.h

@@ -1,7 +1,6 @@
 /* appearance */
 static const int sloppyfocus        = 1;  /* focus follows mouse */
 static const unsigned int borderpx  = 1;  /* border pixel of windows */
-static const int lockfullscreen     = 1;  /* 1 will force focus on the fullscreen window */
 static const float rootcolor[]      = {0.3, 0.3, 0.3, 1.0};
 static const float bordercolor[]    = {0.5, 0.5, 0.5, 1.0};
 static const float focuscolor[]     = {1.0, 0.0, 0.0, 1.0};