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.

Python/asdl.c

@@ -0,0 +1,92 @@
+#include "Python.h"
+#include "asdl.h"
+
+asdl_seq *
+asdl_seq_new(int size)
+{
+	asdl_seq *seq = NULL;
+	size_t n = sizeof(asdl_seq) +
+			(size ? (sizeof(void *) * (size - 1)) : 0);
+
+	seq = (asdl_seq *)PyObject_Malloc(n);
+	if (!seq) {
+		PyErr_SetString(PyExc_MemoryError, "no memory");
+		return NULL;
+	}
+	memset(seq, 0, n);
+	seq->size = size;
+	return seq;
+}
+
+void
+asdl_seq_free(asdl_seq *seq)
+{
+	PyObject_Free(seq);
+}
+
+#define CHECKSIZE(BUF, OFF, MIN) { \
+	int need = *(OFF) + MIN; \
+	if (need >= PyString_GET_SIZE(*(BUF))) { \
+		int newsize = PyString_GET_SIZE(*(BUF)) * 2; \
+		if (newsize < need) \
+			newsize = need; \
+		if (_PyString_Resize((BUF), newsize) < 0) \
+			return 0; \
+	} \
+} 
+
+int 
+marshal_write_int(PyObject **buf, int *offset, int x)
+{
+	char *s;
+
+	CHECKSIZE(buf, offset, 4)
+	s = PyString_AS_STRING(*buf) + (*offset);
+	s[0] = (x & 0xff);
+	s[1] = (x >> 8) & 0xff;
+	s[2] = (x >> 16) & 0xff;
+	s[3] = (x >> 24) & 0xff;
+	*offset += 4;
+	return 1;
+}
+
+int 
+marshal_write_bool(PyObject **buf, int *offset, bool b)
+{
+	if (b)
+		marshal_write_int(buf, offset, 1);
+	else
+		marshal_write_int(buf, offset, 0);
+	return 1;
+}
+
+int 
+marshal_write_identifier(PyObject **buf, int *offset, identifier id)
+{
+	int l = PyString_GET_SIZE(id);
+	marshal_write_int(buf, offset, l);
+	CHECKSIZE(buf, offset, l);
+	memcpy(PyString_AS_STRING(*buf) + *offset,
+	       PyString_AS_STRING(id), l);
+	*offset += l;
+	return 1;
+}
+
+int 
+marshal_write_string(PyObject **buf, int *offset, string s)
+{
+	int len = PyString_GET_SIZE(s);
+	marshal_write_int(buf, offset, len);
+	CHECKSIZE(buf, offset, len);
+	memcpy(PyString_AS_STRING(*buf) + *offset,
+	       PyString_AS_STRING(s), len);
+	*offset += len;
+	return 1;
+}
+
+int 
+marshal_write_object(PyObject **buf, int *offset, object s)
+{
+	/* XXX */
+	return 0;
+}