Add support for ppc-lynxos to GDBserver

[Joel Brobecker]

Hello,

As discussed on IRC, I am submitting these series of patches that
brings support for powerpc-lynxos to GDBserver. As mentioned in
the last patch, this is single-process all-stop support only.

This entire patch series was tested as a whole using a ppc-lynxos cross
GDB hosted on sparc-solaris 2.8.  I ran AdaCore's testsuite, which is
capable of running testcases with gdbserver running on a different
machine than then host.

-- 
Joel