file.c: fix compile error on Linux

* file.c (sys/time.h): include after unistd.h to get rid of
  mismatch on struct stat and some system call functions on Linux.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47886 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2014-10-12

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47887 b2dd03c8-39d4-4d8f-98ff-823fe69b080e