New colormap header file and remove unused functions

The functions related to colormap are moved from funcs.h to the new
file colormap.h. These files are included where needed.

The functions wColormapInstallRoot and wColormapUninstallRoot are
removed, because they are not used.

src/shutdown.c

@@ -36,6 +36,7 @@
 #include "session.h"
 #include "winspector.h"
 #include "wmspec.h"
+#include "colormap.h"
 
 extern Atom _XA_WM_DELETE_WINDOW;
 extern Time LastTimestamp;