Remove rw_lock compatibility code [WIP]

A significant amount of compatible code needed to be added to
support what are now very old kernels.  This patch drops support
for kernels older than 2.6.33, excluding RHEL and SLSE, in
order to simplify the code.

* Removed compatibility code for broken rwsem_is_locked()
  implementation.

* Disabled the rw_tryupgrade() function.  This functionality
  is not strictly required and implementing it correctly
  requires detailed knowledge of the semaphore implementation.
  Because the implementation is subject to change it's safer
  to not provide this support.

* Remove associated configure checks SPL_AC_RWSEM_SPINLOCK_IS_RAW
  and SPL_AC_EXPORTED_RWSEM_IS_LOCKED.

* Fixed all cstyle formating issues.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>