MFC: r228260

MFC: r228260
This patch adds a sysctl to the NFSv4 server which optionally disables the
check for a UTF-8 compliant file name. Enabling this sysctl results in
an NFSv4 server that is non-RFC3530 compliant, therefore it is not enabled
by default. However, enabling this sysctl results in NFSv3 compatible
behaviour and fixes the problem reported by "dan at sunsaturn.com"
to freebsd-current@ on Nov. 14, 2011 under the subject "NFSV4 readlink_stat".

git-svn-id: svn://svn.freebsd.org/base/stable/9@229799 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f