Enable i18n support

As described in #278, having I18n support disabled limits the functionality of
regular expressions.

This commit enables I18n support in the resulting library.

Author: ignisf

ext/libv8/builder.rb

@@ -23,8 +23,7 @@ def gn_args
          v8_use_external_startup_data=false
          target_cpu="#{libv8_arch}"
          v8_target_cpu="#{libv8_arch}"
-         treat_warnings_as_errors=false
-         v8_enable_i18n_support=false).join(' ')
+         treat_warnings_as_errors=false).join(' ')
     end
 
     def generate_gn_args