MGTK: Fix title bar stripes when using 8px font

The commit 258ecee tweaked the title bar appearance, but it only
accounted for the standard 9px tall system font, and that was pure
luck. With an 8px tall font the stripes were drawn differently to the
left and right of the "go away" box.

Fix this properly. This only affects custom builds that use a
different font.

There is a picture of the bad title bars in this comment, but you need
to look closely since there's a menu in the way:
#793 (comment)

mgtk/mgtk.s

@@ -7554,8 +7554,12 @@ stripes_pattern_alt := *+1
         .byte   %00000000
         .byte   %11111111
 
+;;; Also sets `top` and `bottom` using "go away" rect
 .proc SetStripesPattern
         jsr     GetWinGoAwayRect
+        copy16  winrect::y1, top
+        copy16  winrect::y2, bottom
+
         lda     winrect::y1
         and     #1
         beq     :+
@@ -7590,7 +7594,7 @@ stripes_pattern_alt := *+1
 
         jsr     GetWinGoAwayRect
         jsr     FrameWinRect
-        jsr     SetStripesPattern
+        jsr     SetStripesPattern ; also inits `top` and `bottom`
 
         ldax    winrect::x1
         sec
@@ -7605,9 +7609,6 @@ stripes_pattern_alt := *+1
         inx
 :       stax    right
 
-        copy16  winrect::y1, top
-        copy16  winrect::y2, bottom
-
         jsr     PaintRectImpl  ; draws title bar stripes to left of close box
 
 no_goaway:
@@ -7621,7 +7622,7 @@ no_goaway:
         jsr     GetWinTitleBarRect
         jsr     CenterTitleText
         jsr     PenlocToBounds
-        jsr     SetStripesPattern
+        jsr     SetStripesPattern ; also inits `top` and `bottom`
 
         ldax    winrect::x2
         clc