file.c: unpack in binary

* file.c (statfs_fsid): convert with rb_integer_unpack.

* configure.in: fsid_t is no longer used.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45685 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
fix to rescue when test-all runs without installation

https://api.travis-ci.org/jobs/23564212/log.txt?deansi=true

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45686 b2dd03c8-39d4-4d8f-98ff-823fe69b080e