Cleanup of contexts in the full code generator.

src/ast.h

Index: src/ast.h
===================================================================
--- src/ast.h	(revision 5450)
+++ src/ast.h	(working copy)
@@ -172,18 +172,6 @@
 
 class Expression: public AstNode {
  public:
-  enum Context {
-    // Not assigned a context yet, or else will not be visited during
-    // code generation.
-    kUninitialized,
-    // Evaluated for its side effects.
-    kEffect,
-    // Evaluated for its value (and side effects).
-    kValue,
-    // Evaluated for control flow (and side effects).
-    kTest
-  };
-
   Expression() : bitfields_(0) {}
 
   virtual Expression* AsExpression()  { return this; }