Drop dependency from `mruby-rational` to `mruby-object-ext`

mrbgems/mruby-rational/mrbgem.rake

@@ -2,6 +2,4 @@ MRuby::Gem::Specification.new('mruby-rational') do |spec|
   spec.license = 'MIT'
   spec.author  = 'mruby developers'
   spec.summary = 'Rational class'
-
-  spec.add_dependency 'mruby-object-ext', core: 'mruby-object-ext'
 end

mrbgems/mruby-rational/mrblib/rational.rb

@@ -86,7 +86,7 @@ module Kernel
 end
 
 [:+, :-, :*, :/, :<=>, :==, :<, :<=, :>, :>=].each do |op|
-  Fixnum.instance_exec do
+  Fixnum.instance_eval do
     original_operator_name = "__original_operator_#{op}_rational"
     alias_method original_operator_name, op
     define_method op do |rhs|
@@ -97,7 +97,7 @@ end
       end
     end
   end
-  Float.instance_exec do
+  Float.instance_eval do
     original_operator_name = "__original_operator_#{op}_rational"
     alias_method original_operator_name, op
     define_method op do |rhs|