Valgrind gdbserver patch : help needed for linux-arm/s390x/ppc32-64 and MacOS

["Philippe Waroquiers" <philippe.waroquiers@skynet.be>]

I have attached a new version of the Valgrind gdbserver patch in 
https://bugs.kde.org/show_bug.cgi?id=214909

It should work on any x86/amd64 Linux (has been tested with gdb 7.2 on f12-x86, f14-amd64,
ubuntu10.10-x86, red-hat 5.2-amd64).

A previous version has been compiled and manually tested on Macos, so it should not be too difficult
to have it working on MacOS. I had only access during 3 hours to a Mac so for
MacOS, some more "ptrace related" work is needed in vgdb.c to have it fully functional
(i.e. allow gdb to "contact" a process with all threads blocked in a system call).

Linux-arm/s390x/ppc32/ppc64 : in theory, it should compile, and many fucntionalities
should work once compiled (e.g. external command handling, read/write memory,
breakpoints, etc).

To have it fully working (e.g. backtrace, info registers, ...), some (easy) work is needed
(e.g. in valgrind-low-arm.c, valgrind-low-s390x, etc ) to add
a 'switch' mapping the gdb registers to the valgrind registers
and to add a 'dummy call pusher' in vgdb.c.

Any feedback/comment (and help for platforms I do not have access to :) is welcome.

Philippe