Make identifiers str (not str8) objects throughout. This affects the parser, various object implementations, and all places that put identifiers into C string literals. In testing, a number of crashes occurred as code would fail when the recursion limit was reached (such as the Unicode interning dictionary having key/value pairs where key is not value). To solve these, I added an overflowed flag, which allows for 50 more recursions after the limit was reached and the exception was raised, and a recursion_critical flag, which indicates that recursion absolutely must be allowed, i.e. that a certain call must not cause a stack overflow exception. There are still some places where both str and str8 are accepted as identifiers; these should eventually be removed.

--- a/Include/stringobject.h	Sat Jun 09 16:13:23 2007 +0000
+++ b/Include/stringobject.h	Sun Jun 10 09:51:05 2007 +0000
@@ -84,8 +84,8 @@
 #define PyString_CHECK_INTERNED(op) (((PyStringObject *)(op))->ob_sstate)
 
 /* Macro, trading safety for speed */
-#define PyString_AS_STRING(op) (((PyStringObject *)(op))->ob_sval)
-#define PyString_GET_SIZE(op)  (((PyStringObject *)(op))->ob_size)
+#define PyString_AS_STRING(op) (assert(PyString_Check(op)),(((PyStringObject *)(op))->ob_sval))
+#define PyString_GET_SIZE(op)  (assert(PyString_Check(op)),(((PyStringObject *)(op))->ob_size))
 
 /* _PyString_Join(sep, x) is like sep.join(x).  sep must be PyStringObject*,
    x must be an iterable object. */