PR16716 partial fix: Better types in 'syscall.{swapon,syslog}'.

PR16716 partial fix: Better types in 'syscall.{swapon,syslog}'.

* tapset/linux/syscalls2.stp: Fix types in 'syscall.syslog' and
  'syscall.swapon'. In 'syscall.swapon', decode the flags in the new
  'swapflags' variable.
* tapset/linux/nd_syscalls2.stp: In 'nd_syscall.swapon', decode the flags
  in the new 'swapflags' variable.
* tapset/linux/aux_syscalls.stp (_swapon_flags_str): New function.
* tapset/uconversions.stp (user_string_n2_quoted): If we're in a compat
  task, when printing the pointer value as a number, don't expand it to
  64-bits.
* testsuite/systemtap.syscall/swap.c: Added more tests.
* testsuite/systemtap.syscall/syslog.c: New test case.
* testsuite/buildok/syscalls2-detailed.stp: Added new 'swapflags' variable.
* testsuite/buildok/nd_syscalls2-detailed.stp: Ditto.