Add __FILE__, __LINE__ to class-, module_eval calls

[Shamaoke]

Sometimes when exploring or debugging code it's necessary to know where
some method was defined. For this purpose Method#source_location is
used. It reports a filename and a line in the file with a method
definition. However, when using Module#class_eval and
Module#module_eval to dynamically define methods,
the output of Method#source_location is uninformative.

For this reason it's better to add __FILE__ and __LINE__ constants
as the second and third arguments to the aforementioned methods. This
allows Method#source_location to properly locate methods which was
defined dynamically.

Here's some examples:

require 'origin'

class Band
  extend Origin::Forwardable

  select_with :queryable

  def self.queryable
    Object.new.extend Origin::Queryable
  end
end

Band.method(:where).source_location
  # without __FILE__, __LINE__
  #=> ["(eval)", 1]

  # with __FILE__, __LINE__
  #=> ["<...>/lib/origin/forwardable.rb", 53]

require 'origin'

module Finders
  extend Origin::Forwardable

  select_with :queryable

  def queryable
    Object.new.extend Origin::Queryable
  end
end

class Band
  extend Finders
end

Band.method(:where).source_location
  # without __FILE__, __LINE__
  #=> ["(eval)", 1]

  # with __FILE__, __LINE__
  #=> ["<...>/lib/origin/forwardable.rb", 47]

[arthurnn]

I think it should be __LINE__ + 1