[RFA] import drow dbxread.c fix to branch

[Andrew Cagney]

> I'm not sure.  That code assumes a different meaning of line==0 than
> the one we're using.  Particularly, if I understand correctly, the
> meaning in gdbtk comes from a set of Cygnus-internal stabs for handling
> live range splitting, which never made it into any public GCC ...

``Would not be accepted into FSF's official GCC sources?''.  I'm trying 
to find out what the status actually is.

Andrew