git-gui: use themed tk widgets with Tk 8.5

This patch enables the use of themed Tk widgets with Tk 8.5 and above.
These make a significant difference on Windows in making the
application appear native. On Windows and MacOSX ttk defaults to the
native look as much as possible. On X11 the user may select a theme
using the TkTheme XRDB resource class by adding an line to the
.Xresources file. The set of installed theme names is available using
the Tk command 'ttk::themes'. The default on X11 is similar to the current
un-themed style - a kind of thin bordered motif look.

A new git config variable 'gui.usettk' may be set to disable this if
the user prefers the classic Tk look. Using Tk 8.4 will also avoid the
use of themed widgets as these are only available since 8.5.

Some support is included for Tk 8.6 features (themed spinbox and native
font chooser for MacOSX and Windows).

Signed-off-by: Pat Thoyts <patthoyts@users.sourceforge.net>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
diff --git a/lib/console.tcl b/lib/console.tcl
index c112464..1f3248f 100644
--- a/lib/console.tcl
+++ b/lib/console.tcl
@@ -27,20 +27,20 @@
 }
 
 method _init {} {
-	global M1B
+	global M1B use_ttk NS
 
 	if {$is_toplevel} {
-		make_toplevel top w -autodelete 0
+		make_dialog top w -autodelete 0
 		wm title $top "[appname] ([reponame]): $t_short"
 	} else {
-		frame $w
+		${NS}::frame $w
 	}
 
 	set console_cr 1.0
 	set w_t $w.m.t
 
-	frame $w.m
-	label $w.m.l1 \
+	${NS}::frame $w.m
+	${NS}::label $w.m.l1 \
 		-textvariable @t_long  \
 		-anchor w \
 		-justify left \
@@ -78,7 +78,7 @@
 		"
 
 	if {$is_toplevel} {
-		button $w.ok -text [mc "Close"] \
+		${NS}::button $w.ok -text [mc "Close"] \
 			-state disabled \
 			-command [list destroy $w]
 		pack $w.ok -side bottom -anchor e -pady 10 -padx 10
@@ -206,13 +206,14 @@
 }
 
 method _sb_set {sb orient first last} {
+	global NS
 	if {![winfo exists $sb]} {
 		if {$first == $last || ($first == 0 && $last == 1)} return
 		if {$orient eq {h}} {
-			scrollbar $sb -orient h -command [list $w_t xview]
+			${NS}::scrollbar $sb -orient h -command [list $w_t xview]
 			pack $sb -fill x -side bottom -before $w_t
 		} else {
-			scrollbar $sb -orient v -command [list $w_t yview]
+			${NS}::scrollbar $sb -orient v -command [list $w_t yview]
 			pack $sb -fill y -side right -before $w_t
 		}
 	}