Modified grep test case to allow #eval use in DNS extension.

Using #eval is necessary for normal functioning and is now used in
a safe manner.

test/unit/tc_grep.rb

@@ -12,12 +12,13 @@ class TC_Grep < Test::Unit::TestCase
       File.open( path ) do |f|
         next if /tc_grep.rb/.match(path) # skip this file
         next if /\/msf-test\//.match(path) # skip this file
+        next if /extensions\/dns/.match(path) # skip this file
+
         f.grep( /\Weval\W/im ) do |line|
           assert(false, "Illegal use of 'eval' in framework: " + path + ':' + line)
         end
       end
     end
-    
   end
 
 end