Create R_PAGER_FLOW config variable flag.

Create R_PAGER_FLOW config variable flag.

Use this for $header_color_partial, $markers, and $smart_wrap.  When
these options are changed in the pager, this flag will force a
recalculation of lineInfo.

Remove the manual checks in OP_ENTER_COMMAND for $markers and
$smart_wrap, and instead use the same REDRAW_FLOW processing used for
a SigWinch.