error.c: rb_sys_fail_path_in

* error.c (syserr_initialize): add optional function name.

* error.c (rb_sys_fail_path_in): rename and move from file.c, and pass
  func_name to SystemCallError#initialize.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39763 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* test/rubygems/test_gem_package.rb (test_verify_nonexistent): should
  make no assumptions on system error messages.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39764 b2dd03c8-39d4-4d8f-98ff-823fe69b080e