Anyway, below is a first hack at the autoconf tests. The tests
themselves are inspired by the standard AC_FUNC_CLOSEDIR_VOID and
AC_FUNC_SELECT_ARGTYPES tests. My code defines PTRACE_LONG if the
return type of ptrace(2) is `long', defines PTRACE_TYPE_ARG3 to the
type of the third argument of ptrace(2) and defines PTRACE_TYPE_ARG5
to the type of the fifth argument of ptrace(2) if it has one.
PTRACE_TYPE_ARG3 will replace PTRACE_ARG3_TYPE. PTRACE_XFER_TYPE will
be set based on PTRACE_LONG and PTRACE_TYPE_ARG5 will replace
FIVE_ARG_PTRACE.