Windows: fixup gettmpdir()

Windows: fixup gettmpdir()

Use InterlockedCompareExchangePointer for hostparse()
instead of fudging it and leaking memory.

If the max path length is MAX_PATH must allocate MAX_PATH+1.

Reviewed-on: http://gerrit.openafs.org/3658
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from commit a61a719d35cd6008f35c4f5cb8aaa83453d1d8c1)

Change-Id: I2183cd52298ea1d1204102fee66dea4755de3b41
Reviewed-on: http://gerrit.openafs.org/3820
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>