dfamust turns on the flag when a state exactly matches the proposed one.
However, when the state has begline and/or endline constraints, turns
off it.

This patch enables to match a state exactly, even if the state has
begline and/or endline constraints.  If a exact string has one of their
constrations, the string adding eolbyte to a head and/or foot is pushed
to kwsincr().  In addition, if it has begline constration, start
searching from just before the position of the text.

Norihiro