internal.h: rb_syserr_fail_path

* error.c (rb_syserr_fail_path_in): new function split from
  rb_sys_fail_path_in to raise SystemCallError without errno.
* internal.h (rb_syserr_fail_path): like rb_sys_fail_path but without
  errno.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43372 b2dd03c8-39d4-4d8f-98ff-823fe69b080e