Merge from ast-arena.  This reduces the code in Python/ast.c by ~300 lines,
simplifies a lot of error handling code, and fixes many memory leaks.
diff --git a/Python/asdl.c b/Python/asdl.c
index 07ad4b3..ccd8714 100644
--- a/Python/asdl.c
+++ b/Python/asdl.c
@@ -2,17 +2,18 @@
 #include "asdl.h"
 
 asdl_seq *
-asdl_seq_new(int size)
+asdl_seq_new(int size, PyArena *arena)
 {
 	asdl_seq *seq = NULL;
 	size_t n = sizeof(asdl_seq) +
 			(size ? (sizeof(void *) * (size - 1)) : 0);
 
-	seq = (asdl_seq *)PyObject_Malloc(n);
+	seq = (asdl_seq *)malloc(n);
 	if (!seq) {
 		PyErr_NoMemory();
 		return NULL;
 	}
+        PyArena_AddMallocPointer(arena, (void *)seq);
 	memset(seq, 0, n);
 	seq->size = size;
 	return seq;
@@ -21,6 +22,4 @@
 void
 asdl_seq_free(asdl_seq *seq)
 {
-	PyObject_Free(seq);
 }
-