Segregated symbols into 5 separate namespaces

The different namespaces are:

  Function      Value expression functions, which receive a "context"
  Option        Command-line options
  Precommand    Commands which are invoked before reading the journal
  Command       Commands which are invoked after reading the journal
  Directive     Directives that occur at column 0 in a data file

This greatly eases the ability for Python uses to add intercept hooks to
change how the basic Ledger module functions.  An example of what should
be possible soon:

  import ledger

  def my_foo_handler(value):
      print "--foo received:", value

  ledger.add_handler(ledger.Option, "foo=", my_foo_handler)

1 files changed, 2 insertions, 1 deletions

diff --git a/src/session.h b/src/session.h
index 58e33f6b..972a97ba 100644
--- a/src/session.h
+++ b/src/session.h
@@ -116,7 +116,8 @@ public:
 
   option_t<session_t> * lookup_option(const char * p);
 
-  virtual expr_t::ptr_op_t lookup(const string& name);
+  virtual expr_t::ptr_op_t lookup(const symbol_t::kind_t kind,
+				  const string& name);
 
   /**
    * Option handlers