Merge ast-branch to head

This change implements a new bytecode compiler, based on a
transformation of the parse tree to an abstract syntax defined in
Parser/Python.asdl.

The compiler implementation is not complete, but it is in stable
enough shape to run the entire test suite excepting two disabled
tests.

Objects/frameobject.c

@@ -3,6 +3,7 @@
 
 #include "Python.h"
 
+#include "code.h"
 #include "compile.h"
 #include "frameobject.h"
 #include "opcode.h"