Remove NilClass whiners feature.

Removing this feature causes boost in performance when using Ruby 1.9.

Ruby 1.9 started to do implicit conversions using `to_ary` and `to_str`
in some STDLIB methods (like Array#join). To do such implicit conversions,
Ruby 1.9 always dispatches the method and rescues the NoMethodError exception
in case one is raised.

Therefore, since the whiners feature defined NilClass#method_missing, such
implicit conversions for nil became much, much slower. In fact, just defining
NilClass#method_missing (even without the whiners feature) already causes a
massive slow down. Here is a snippet that shows such slow down:

    require "benchmark"
    Benchmark.realtime { 1_000.times { [nil,nil,nil].join } }

    class NilClass
      def method_missing(*args)
        raise NoMethodError
      end
    end

    Benchmark.realtime { 1_000.times { [nil,nil,nil].join } }

1 files changed, 0 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 7ba585b8e0..58d23d2f78 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -2222,8 +2222,6 @@ MSG
     include AutosaveAssociation, NestedAttributes
     include Aggregations, Transactions, Reflection, Serialization, Store
 
-    NilClass.add_whiner(self) if NilClass.respond_to?(:add_whiner)
-
     # Returns the value of the attribute identified by <tt>attr_name</tt> after it has been typecast (for example,
     # "2004-12-12" in a data column is cast to a date object, like Date.new(2004, 12, 12)).
     # (Alias for the protected read_attribute method).