* hurd/intr-msg.c: Use INTR_MSG_TRAP macro from machine-dependent
"intr-msg.h" for special syscall code, instead of i386-specific asm.
* hurd/hurdsig.c: Use INTR_MSG_BACK_OUT macro from
machine-dependent "intr-msg.h" before mutating thread state to
skip RPC.
* sysdeps/mach/hurd/i386/trampoline.c: If PC is inside
_hurd_intr_rpc_mach_msg special syscall code, use real SP saved in
%ecx.
* Makeconfig (link-libc): New variable; use shared library if
available.
(+link): Use it.
* sysdeps/mach/hurd/fork.c (_hurd_fork_locks): Variable removed.
Instead, declare with `symbol_set_declare'.
(fork): Use symbol_set_* macros for _hurd_fork_locks.
Use SS->thread instead of __mach_thread_self (). Suspend all
other threads during task_create and port copying.