* verify.cc (state::seen_subrs): New field.
	(state::state): Initialize it.
	(state::clean_subrs): New method.
	(state::~state): Call it.
	(state::copy): Copy subroutine list.
	(state::add_subr): New method.
	(state::merge): Only register a change if the current subroutine
	hasn't yet been noted.

From-SVN: r62878