updated for version 7.3.829

Problem:    When compiled with the +rightleft feature 'showmatch' also shows a
            match for the opening paren.  When 'revins' is set the screen may
            scroll.
Solution:   Only check the opening paren when the +rightleft feature was
            enabled.  Do not show a match that is not visible. (partly by
            Christian Brabandt)