Linux CM: Use kernel allocator directly for events

Linux CM: Use kernel allocator directly for events

When allocating memory for our events system, use the kernel
allocator directly, rather than going via our shim. This is much
more efficient, but has the drawback that we are now responsible
for freeing our own memory, rather than it all being magically
given back upon shutdown.

Change-Id: I9cb31e4c6b5b4ff2497b627e7ab87716e6da6fa9
Reviewed-on: http://gerrit.openafs.org/4751
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>