* exec/trace.c (check_signal): New function.
(handle_exec, process_system_call): Handle signal-delivery-stop
while waiting synchronously for syscall completion.
* exec/config.h.in: Autoheader.
* exec/configure.ac: Check for siginfo_t.si_syscall.
* exec/trace.c (exec_waitpid): If SIGSYS is received, and caused by
seccomp, drop it should the call number be the invalid system call
used by Emacs.
* exec/config.h.in: Autoheader.
* exec/configure.ac: Use system extensions.
(HAVE_PROCESS_VM): Define if process_vm_readv and
process_vm_writev are available.
* exec/trace.c (read_memory, user_copy): Implement in terms of
process_vm if possible.
* exec/config.h.in (__bool_true_false_are_defined):
* exec/configure.ac (REENTRANT): New definition.
(READLINKAT_SYSCALL, READLINK_SYSCALL): New defines. Set on all
hosts.
* exec/exec.c (MIN, MAX): Remove redundant declarations. Move
to config.h.
(exec_0): Copy name of executable into NAME when !REENTRANT.
* exec/exec.h (struct exec_tracee): New struct `exec_file'.
* exec/trace.c (remove_tracee, handle_exec, handle_readlinkat)
(process_system_call, after_fork): Handle readlinkat system
calls.
