Refactor Class#get_members.

Instead of adding two different sets of keys to one hash, build the
hash just by member name.  Look member name up from hash and filter
by type if needed.

Doing things in this more correct way brought up some bugs in other
places. Like {@link #foo-bar} being detected as link to member foo
of type bar, which happened to work. Now we only detect correct types.

Similarly the @inheritdoc happened to work because string interpolation
handles both symbols and strings equally well. Now it needs to be
converted to symbol explicitly.

All-in-all we now have more correct implementation.