mips ptrace.S fix

[C. Jayachandran]

The ptrace system call implementation seems to have a bug, we need to
save ra and gp before calling the __error, and that will need a stack
frame.

I've attached a patch that should fix this for o32 ABI - but it really
should be written with ABI-independent macros, any clue on how to do
this which will take care of n32/64 too will be helpful.

I also have some initial patches for making gdb work on MIPS. . That
patch is also attached, but it is work in progress, only the static
executables work now.

JC.