[RFA] stabs: octal negative numbers

[Joel Brobecker]

> Tested on an i686-linux host, with stabs+ format, no regressions.
> Worth submitting an Ada test case, I guess.

Speaking of Ada testcases, it might be time now to revisit how we
organize the gdb.ada subdirectory, because the current approach is
not going to scale well. I had a short private discussion with
Michael C about this, just to let him know that I was thinking
about this. I'll add this task on my TODO list.

-- 
Joel