mount.nfs: Support double-wide characters in printed strings

Previous NLS changes missed a spot or two.  This patch tries to get
most of them, but probably misses a few more.

In errors.c:mount_errors() I've removed a period at the end of the error
messages; this is consistent with other error messages I've examined.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Neil Brown <neilb@suse.de>