git-gui: themed.tcl: use full namespace for color

Tcl 9 imposes strict requirements on namespaces for variables, while Tcl
8 does not. lib/themed.tcl does not use the fully qualified name for the
"color" namespace, with result that variables are not found with Tcl
9.0. Fix this.

Signed-off-by: Mark Levedahl <mlevedahl@gmail.com>

Author: mark987

lib/themed.tcl

@@ -21,10 +21,10 @@ namespace eval color {
 		set inactive_select_bg	[convert_rgb_to_gray $select_bg]
 		set inactive_select_fg	$select_fg
 
-		set color::select_bg $select_bg
-		set color::select_fg $select_fg
-		set color::inactive_select_bg $inactive_select_bg
-		set color::inactive_select_fg $inactive_select_fg
+		set ::color::select_bg $select_bg
+		set ::color::select_fg $select_fg
+		set ::color::inactive_select_bg $inactive_select_bg
+		set ::color::inactive_select_fg $inactive_select_fg
 
 		proc add_option {key val} {
 			option add $key $val widgetDefault