+20180908
+ + document --with-pcre2 configure option in INSTALL.
+ + improve workaround for special case in PutAttrChar() where a cell is
+ marked as alternate-character set, to handle a case where the
+ character in the cell does not correspond to any of the ASCII
+ fallbacks (report by Leon Winter, cf: 20180505).
+ + amend change to form library which attempted to avoid unnecessary
+ update of cursor position in non-public fields, to simply disable
+ output in this case (patch by Leon Winter, cf: 20180414).
+ + improve check for LINE_MAX runtime limit, to accommodate broken
+ implementations of sysconf().
+