[patch] Fix -readnow for -gdwarf-4 unused type units

[Tom Tromey]

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

Jan> currently -readnow on -gdwarf-4 files often crashes GDB if any of the type
Jan> units are unused (which happens).  There are two kinds of crashes.

Jan> I find the offset field was duplicate and in some cases uninitialized.

Jan> No regressions on {x86_64,x86_64-m32,i686}-fedora15-linux-gnu with -gdwarf-4.

This looks good to me.
I think you should check it in.

Tom