Expressions reboot

- Created A3.{h,cpp} which will be a simpler, lightweight version of
  Arguments.{h,cpp} that does less, but does it better.
- Created E9.{h,cpp} which will be a better implementation of
  Expression.{h,cpp} that does less, but does it better.
- Integrated A3 into Context::initialize, and Arguments and A3 will
  coexist until A3 surpasses Arguments.

src/E9.h

@@ -0,0 +1,73 @@
+////////////////////////////////////////////////////////////////////////////////
+// taskwarrior - a command line task list manager.
+//
+// Copyright 2006 - 2011, Paul Beckingham, Federico Hernandez.
+// All rights reserved.
+//
+// This program is free software; you can redistribute it and/or modify it under
+// the terms of the GNU General Public License as published by the Free Software
+// Foundation; either version 2 of the License, or (at your option) any later
+// version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+// details.
+//
+// You should have received a copy of the GNU General Public License along with
+// this program; if not, write to the
+//
+//     Free Software Foundation, Inc.,
+//     51 Franklin Street, Fifth Floor,
+//     Boston, MA
+//     02110-1301
+//     USA
+//
+////////////////////////////////////////////////////////////////////////////////
+#ifndef INCLUDED_E9
+#define INCLUDED_E9
+#define L10N                                           // Localization complete.
+
+#include <string>
+#include <stack>
+#include <Arguments.h>
+#include <Task.h>
+#include <RX.h>
+#include <Variant.h>
+
+class E9
+{
+public:
+  E9 (Arguments&);
+  ~E9 ();
+  bool eval (const Task&);
+  bool evalFilter (const Task&);
+  std::string evalE9 (const Task&);
+  void eval (const Task&, std::vector <Variant>&);
+
+private:
+  void expand_sequence ();
+  void implicit_and ();
+  void expand_tag ();
+  void expand_pattern ();
+  void expand_attr ();
+  void expand_attmod ();
+  void expand_word ();
+  void expand_tokens ();
+  void postfix ();
+
+  void tokenize (const std::string&, const std::string&, std::vector <std::string>&, Arguments&);
+  void create_variant (Variant&, const std::string&, const std::string&);
+  bool is_new_style ();
+
+private:
+  bool eval_match (Variant&, Variant&, bool);
+
+private:
+  Arguments _args;
+  std::map <std::string, RX> _regexes;
+  bool _prepared;
+};
+
+#endif
+////////////////////////////////////////////////////////////////////////////////