Fix C++ compilation of the Hurd port

[Thomas Schwinge]

Hi!

I hear, GDB is now a C++ code base?  ;-) (Actually, to the best of my
knowledge, that makes GDB the first C++ project to use low-level
Mach/Hurd interfaces.)

No doubt this will need to be polished some more, but to at least restore
the build, I committed the following five patches to fix C++ compilation
of the Hurd port.


Grüße
 Thomas