gitk: Skip translation of "wrong Tcl version" message

We check the required Tcl version number before we setup msgcat for
language translation.  If the Tcl version is too old just display the
untranslated error text.

The caller of show_error can now pass an alternative function for mc.
The Tcl list function turns the translation into a no-op.

This fixes the error:
    Error in startup script: invalid command name "mc"
when attempting to start gitk with Tcl 8.3.

Tested with both Tcl 8.3 and 8.4.

Signed-off-by: Bernt Hansen <bernt@norang.ca>
Signed-off-by: Paul Mackerras <paulus@samba.org>

gitk

@@ -1787,10 +1787,10 @@ proc make_transient {window origin} {
     }
 }
 
-proc show_error {w top msg} {
+proc show_error {w top msg {mc mc}} {
     message $w.m -text $msg -justify center -aspect 400
     pack $w.m -side top -fill x -padx 20 -pady 20
-    button $w.ok -text [mc OK] -command "destroy $top"
+    button $w.ok -text [$mc OK] -command "destroy $top"
     pack $w.ok -side bottom -fill x
     bind $top <Visibility> "grab $top; focus $top"
     bind $top <Key-Return> "destroy $top"
@@ -11034,8 +11034,8 @@ proc get_path_encoding {path} {
 
 # First check that Tcl/Tk is recent enough
 if {[catch {package require Tk 8.4} err]} {
-    show_error {} . [mc "Sorry, gitk cannot run with this version of Tcl/Tk.\n\
-		     Gitk requires at least Tcl/Tk 8.4."]
+    show_error {} . "Sorry, gitk cannot run with this version of Tcl/Tk.\n\
+		     Gitk requires at least Tcl/Tk 8.4." list
     exit 1
 }