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, 6 insertions, 2 deletions

diff --git a/src/xact.cc b/src/xact.cc
index 3291c5be..473837b6 100644
--- a/src/xact.cc
+++ b/src/xact.cc
@@ -422,8 +422,12 @@ namespace {
   }
 }
 
-expr_t::ptr_op_t xact_t::lookup(const string& name)
+expr_t::ptr_op_t xact_t::lookup(const symbol_t::kind_t kind,
+				const string& name)
 {
+  if (kind != symbol_t::FUNCTION)
+    return item_t::lookup(kind, name);
+
   switch (name[0]) {
   case 'c':
     if (name == "code")
@@ -448,7 +452,7 @@ expr_t::ptr_op_t xact_t::lookup(const string& name)
     break;
   }
 
-  return item_t::lookup(name);
+  return item_t::lookup(kind, name);
 }
 
 bool xact_t::valid() const