PR16716 partial fix: Fix types in syscall.epoll_{create,ctl,pwait,wait}.

PR16716 partial fix: Fix types in syscall.epoll_{create,ctl,pwait,wait}.

* tapset/linux/syscalls.stp (syscall.epoll_create): Fix types.
  (syscall.epoll_ctl): Ditto.
  (syscall.epoll_wait): Ditto.
  (syscall.epoll_pwait): Add convenience variables.
* tapset/linux/nd_syscalls.stp: Ditto.
* tapset/linux/aux_syscalls.stp (_opoll_op_str): Updated and improved.
  (_epoll_create1_flag_str): Ditto.
* runtime/linux/compat_unistd.h: Added __NR_compat_epoll_wait.
* testsuite/buildok/syscalls-detailed.stp: Add test for new epoll_pwait
  convenience variables.
* testsuite/buildok/nd_syscalls-detailed.stp: Ditto.
* testsuite/systemtap.syscall/poll.c: Add more error testing.