Windows: conditionalize mappings of error values

Windows: conditionalize mappings of error values

Visual Studio 10 adds a large number of additional POSIX C99
error values to errno.h.  Wrap each mapping with #ifndef to ensure
that we do not redefine the C runtime errno.h definition.

Reviewed-on: http://gerrit.openafs.org/5129
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
(cherry picked from f631a11f5e9ab50e62b3aaebbff9ef200ac799fe)

Change-Id: I528547f95ebbe83390924844d21a9e850dc5967d
Reviewed-on: http://gerrit.openafs.org/5148
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>