[Sass] Fix a Ruby 1.9 compatibility error.

lib/sass/script/funcall.rb

@@ -42,7 +42,7 @@ module Sass
 
         return Functions::EvaluationContext.new(environment.options).send(name, *args)
       rescue ArgumentError => e
-        raise e unless e.backtrace.first =~ /:in `(#{name}|perform)'$/
+        raise e unless e.backtrace.first =~ /:in `(block in )?(#{name}|perform)'$/
         raise Sass::SyntaxError.new("#{e.message} for `#{name}'")
       end
     end

test/test_helper.rb

@@ -7,7 +7,7 @@ $:.unshift lib_dir unless $:.include?(lib_dir)
 require 'haml'
 require 'sass'
 
-Sass::RAILS_LOADED = true
+Sass::RAILS_LOADED = true unless defined?(Sass::RAILS_LOADED)
 
 # required because of Sass::Plugin
 unless defined? RAILS_ROOT