Uses <asm/syscall.h> when available.

Uses <asm/syscall.h> when available.
2009-04-09  David Smith  <dsmith@redhat.com>

        * buildrun.cxx (compile_pass): Compile autoconf test for
        <asm/syscall.h>.
        * runtime/autoconf-asm-syscall.c: New "autoconf" test the presence
        of <asm/syscall.h>.
        * runtime/syscall.h: If <asm/syscall.h> exists, use it.
        Otherwise, use our private copy of the functions for each
        architecture.
        (syscall_get_nr): Renamed from __stp_user_syscall_nr().
        (syscall_get_return_value): Renamed from
        __stp_user_syscall_return_value().
        (syscall_get_arguments): Renamed from __stp_user_syscall_arg().
        * runtime/task_finder.c
        (__stp_utrace_task_finder_target_syscall_exit): Uses new syscall.h
        functions.
        * tapset/utrace.stp: Ditto.