Import CSV 3.0.8

This includes performance improvements and backward incompatibility
fixes.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67560 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/csv/writer.rb

@@ -18,6 +18,7 @@ class CSV
       if @options[:write_headers] and @headers
         self << @headers
       end
+      @fields_converter = @options[:fields_converter]
     end
 
     def <<(row)
@@ -31,6 +32,8 @@ class CSV
       @headers ||= row if @use_headers
       @lineno += 1
 
+      row = @fields_converter.convert(row, nil, lineno) if @fields_converter
+
       converted_row = row.collect do |field|
         quote(field)
       end