dtrace: support building on UEK4

dtrace: support building on UEK4

Support building DTrace modules on UEK4.  Various things changed at
the kernel level between UEK3 and UEK4 that require adjustments in the
building of the DTrace modules.

- ARCH no longer reflects the difference between x86 and x86_64.  So,
  we now use UTS_MACHINE to drive the architecture-specific portions
  of DTrace during the building process.

- The trick used to implement a direct call probe in dt_test_probe()
  required updating to avoid compiler warnings/errors.  It is a little
  bit less "ugly" now :)

- The uid and gid used in the task structure now uses kuid_t and kgid_t
  as datatypes, which are no longer numeric values but rather a struct.

- The API for the IDR facility in the Linux kernel changed.

- The flush_delayed_work_sync() function has been removed.  Source code
  has been updated to use flush_delayed_work().

- The mechanism to enforce turning preemption on and off has been
  updated.

Orabug: 20456825

Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Acked-by: Nick Alcock <nick.alcock@oracle.com>