* configure.in: check struct statvfs and struct statvfs.f_fstypename.

* configure.in: on NetBSD fstatfs is obsoleted.

* file.c: support NetBSD for File::Statfs.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45733 b2dd03c8-39d4-4d8f-98ff-823fe69b080e