Explicit representation of ASTs for all the functions in a compile unit.

Added AST and Function classes.
Now, we parse the whole file and build up the AST for all of the
  functions in the Module before we emit IR for the functions (vs. before,
  when we generated IR along the way as we parsed the source file.)

ctx.h

@@ -59,14 +59,15 @@ struct CFInfo;
 class FunctionEmitContext {
 public:
     /** Create a new FunctionEmitContext.
-        @param returnType   The return type of the function
-        @param function     LLVM function in the current module that corresponds
+        @param function     The Function object representing the function
+        @param sym          Symbol that corresponds to the function
+        @param llvmFunction LLVM function in the current module that corresponds
                             to the function
-        @param funSym       Symbol that corresponds to the function
         @param firstStmtPos Source file position of the first statement in the
                             function
      */
-    FunctionEmitContext(const Type *returnType, llvm::Function *function, Symbol *funSym,
+    FunctionEmitContext(Function *function, Symbol *funSym, 
+                        llvm::Function *llvmFunction,
                         SourcePos firstStmtPos);
     ~FunctionEmitContext();
 
@@ -86,6 +87,8 @@ public:
     /** Returns the current mask value */ 
     llvm::Value *GetMask();
 
+    void SetMaskPointer(llvm::Value *p);
+
     /** Provides the value of the mask at function entry */
     void SetEntryMask(llvm::Value *val);