Fix bug reported by Jurgen Bollerhey

I have a
"REM Mon SPECIAL WEEK (W[weekno()])"
in my reminders file.
With tkremind -m the week number is displayed on the 2nd column which is
Tuesday and the date of this Tuesday is taken from the monday of the
next week, sometimes of Monday the same week.

scripts/tkremind

@@ -962,7 +962,8 @@ proc FillCalWindow {} {
 	    "WEEK" {
 		set stuff [string trimleft $stuff]
 		set stuff [string trimright $stuff]
-		set label [expr $firstWkday + $day - 1]
+		set offset [CalEntryOffset $firstWkday]
+		set label [expr $offset + $day]
 		.cal.l$label configure -text "$day $stuff"
 		continue
 	    }