[RFC/ia64] link against libunwind rather than using dlopen

[Tom Tromey]

>>>>> "Jan" == Jan Kratochvil <jan.kratochvil@redhat.com> writes:

Jan> The gdb binary years ago could be freely copied across hosts and it
Jan> still worked.
[...]
Jan> Unfortunately since DT_NEEDED libpython this feature is already lost so it
Jan> should be OK now even for libunwind.so.7.

We could make this work if we truly wanted to.  It just seems like a lot
of effort; and building gdb is not so very hard.

The other day I was thinking we could even automate it by reading the
libpython debuginfo to generate weak declarations for the public API :-)
But, ok, that is not practical for regular gdb builds.

Tom