Windows: prevent buffer overrun in cklog

Windows: prevent buffer overrun in cklog

The Windows version of klog.exe will overwrite the realm and
password buffers if the command line input is too long.  Generate
an error and terminate the program instead.

Change-Id: I80671adcf92e9140f14a943b2677a352d2223eee
Reviewed-on: http://gerrit.openafs.org/2558
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Tested-by: Jeffrey Altman <jaltman@openafs.org>