fixes entry for pull request #673 - incomplete map

Sometimes tty left part of the screen blank after covering the entire
screen with a menu and then switching to a smaller menu that should
have redrawn the map as background.  To reproduce:
|    O     - puts up a big menu
|    :     - enter a search string: "autopickup exception"
| <return> - dismiss the menu after the search makes one match
The autopickup exceptions sub-menu will be shown, with a small border
of map around it but most of the screen blank.  (This behavior was
present before 3.6.0 but may not have been noticed because when the
discovered map doesn't extend to the corner menu's area, the blank
map probably seemed to be intentional.  But if a fringe of map gets
drawn around the menu, that clearly isn't intended.)  The incomplete
map is temporary; once menu is dismissed, it gets redrawn properly.

This adds a flush_screen() call after one particular docrt() call.
Perhaps docrt() should end with its own flush_screen() instead, but
that would require a lot more testing.

Closes #673

doc/fixes3-7-0.txt

@@ -1211,6 +1211,9 @@ tiles: add indicator of thonged portion to aklys tile
 tty: role and race selection menus weren't filtering out potential choices
 	which got excluded by OPTIONS=align:!lawful or !neutral or !chaotic
 tty: '$' can now select gold in a menu even when it isn't on current page
+tty: if a menu used full screen and brought up another menu that wasn't full
+	screen, sometimes only a small border of background was drawn around
+	it with most of the map left blank until after the menu was dismissed
 Unix: when user name is used as default character name, keep hyphenated value
 	intact instead stripping off dash and whatever follows as if that
 	specified role/race/&c (worked once upon a time; broken since 3.3.0)