used to get and set the thread user value, which is an opaque pointer to
a per thread structure stored in userland. cthread_self() is used by Darwin
as an implementation for pthread_self(), which return the thread id.
We use the p_emuldata field of struct proc in order to keep track of the
thread user value. For now the value is per-process, but we will make it
per-thread when we will take care of threading.
While we are there, do some KNF
ppccalls, with system call numbers starting at 0x6000
fasttraps, with system call numbers starting at 0x7FF0
Because the Mach system call dispatching code has grown a bit
too much, introduce an inline function to handle it (mach_syscall_dispatch).
While we are there, remove the Mach and Linux includes from
arch/powerpc/powerpc/syscall.c and push them into
arch/powerpc/powerpc/{mach|linux}_syscall.c
