ARel 1.9.2 compatibility

1. Array#to_s in 1.9.2 changed to more :inspect-like,

--- a/lib/arel/engines/sql/relations/relation.rb
+++ b/lib/arel/engines/sql/relations/relation.rb 
@@ -12,7 +12,7 @@
         order = order.zip((0...order.size).to_a).map { |s,i| "id_list.alias_#{i} #{'DESC' if s =~ /\bdesc$/i}" }.join(', ')

         query = build_query \
-          "SELECT     #{select_clauses.to_s}",
+          "SELECT     #{select_clauses.kind_of?(::Array) ? select_clauses.join("") : select_clauses.to_s}",
           "FROM       #{table_sql(Sql::TableReference.new(self))}",
           (joins(self)                                   unless joins(self).blank? ),
           ("WHERE     #{where_clauses.join("\n\tAND ")}" unless wheres.blank?      ),

1. Some methods aren't delegated, as instance_methods() returns array of symbols:

--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -110,7 +110,7 @@ module ActiveRecord
     end

     def respond_to?(method)
-      if @relation.respond_to?(method) || Array.instance_methods.include?(method.to_s)
+      if @relation.respond_to?(method) || [].respond_to?(method)
         true
       else
         super
@@ -121,7 +121,7 @@ module ActiveRecord
       def method_missing(method, *args, &block)
         if @relation.respond_to?(method)
           @relation.send(method, *args, &block)
-        elsif Array.instance_methods.include?(method.to_s)
+        elsif [].respond_to?(method)
           to_a.send(method, *args, &block)
         end
       end