rx: fix rx_atomic warnings under Solaris

rx: fix rx_atomic warnings under Solaris

The Solaris implementation of the rx_atomic functions generate numerous
complile time warnings due to an integer type mismatch.

  "rx_atomic.h", line xxx: warning: argument #1 is incompatible with prototype:

The rx_atomic_t is an unsigned int under Solaris, however the Solaris
atomic_set_long_excl and atomic_clear_long_excl functions take a ulong_t type
Solaris does not provide 'unsigned int' variants of these two functions.

Fortunately, ulong_t variants of all the atomic we need for rx are available,
in current as well as older versions of Solaris, so convert the Solaris
rx_atomic_t type to be a ulong_t and convert all of the Solaris atomic calls to
the ulong_t variants to avoid integer type mismatches.

Change-Id: Ib54ca4bb8b9f044684301f0fb7971aec223e5993
Reviewed-on: https://gerrit.openafs.org/12991
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>