[RFA] Check for dladdr in gdbserver

[Joel Brobecker]

Not enough experience with the gdbserver code, especially on Linux
targets, so can't really review the patch itself, even if it looks OK
to me. However:

> NOTE: There's similar code in gdb/linux-thread-db.c but it isn't
> compiled for android (android is a cross target) so I didn't change it.
> I can add a similar patch there if required.

IMO: I would leave it be until it because a bona fide issue (when
someone tries to port GDB to a Linux system without a glibc).

-- 
Joel