Added rename()/renameat() testcase and prevent more syscall nesting.

Added rename()/renameat() testcase and prevent more syscall nesting.

* testsuite/systemtap.syscall/rename.c: New testcase for rename() and
  renameat().
* tapset/linux/syscalls2.stp: Prevent syscall nesting in syscall.open,
  and syscall.renameat.
* tapset/linux/nd_syscalls2.stp: Ditto.
* tapset/linux/syscalls.stp: Prevent syscall nesting in syscall.mkdirat.
* tapset/linux/nd_syscalls.stp: Ditto.
* runtime/linux/compat_unistd.h: Add __NR_compat defines.