[PATCH 0/4] Handle copy relocations and add $_ada_exception

[Tom Tromey]

This series adds support for $_ada_exception -- a convenience variable
that holds the address of the exception currently being thrown by the
Ada runtime.  This is analogous to the existing $_exception variable
that is used for C++.

Earlier, I checked in a patch to change how Ada exception catchpoints
handle the case where an exception symbol occurs in multiple objfiles.
This same problem affected $_ada_exception.  After one other failed
attempt to fix the problem, I ended up trying to fix the copy
relocation problem in a more principled way.  That is patch #2 here.

Regression tested on x86-64 Fedora 29.

Tom