Make appsimpl also simplify dataconstructors.

Make appsimpl also simplify dataconstructors.

These were previously left alone, since they were considered already
simple (they're simple variable references). However, a dataconstructor
can be translated to a VHDL expression, which can be assigned to a signal,
but not used in the port map of an component instantiation.

Also prevent letremovetop from inlining the datacon again.