Refine Ada overload matching

Refine Ada overload matching

Currently, the overload handling in Ada assumes that any two array
types are compatible.  However, this is obviously untrue, and a user
reported an oddity where comparing two Ada strings resulted in a call
to the "=" function for packed boolean arrays.

This patch improves the situation somewhat, by requiring that the two
arrays have the same arity and compatible base element types.  This is
still over-broad, but it seems safe and is better than the status quo.