Windows: Add CODESIGN_OTHER option to make signtool rules

Windows: Add CODESIGN_OTHER option to make signtool rules

Some organizations may need to pass additional parameters to
signtool.exe.  Add the optional CODESIGN_OTHER value to permit
arbitrary additional parameters to be specified.

Change-Id: I225a790e04d8aa1298bbf03a9559ae0b5e63a70d
Reviewed-on: http://gerrit.openafs.org/3322
Tested-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-on: http://gerrit.openafs.org/4230