exposed in header files.  Fixed a few comments in these headers.

As we might have expected, writing down invariants systematically exposed a
(minor) bug.  In this case, function objects have a writeable func_code
attribute, which could be set to code objects with the wrong number of
free variables.  Calling the resulting function segfaulted the interpreter.
Added a corresponding test.

__module__ is the string name of the module the function was defined
in, just like __module__ of classes.  In some cases, particularly for
C functions, the __module__ may be None.

Change PyCFunction_New() from a function to a macro, but keep an
unused copy of the function around so that we don't change the binary
API.

Change pickle's save_global() to use whichmodule() if __module__ is
None, but add the __module__ logic to whichmodule() since it might be
used outside of pickle.

Thanks to Skip Montanaro and Kalle Svensson for the patches.

method types.

The majority of the changes are in the compiler.  The mainloop changes
primarily to implement the new opcodes and to pass a function's
closure to eval_code2().  Frames and functions got new slots to hold
the closure.

Include/compile.h
    Add co_freevars and co_cellvars slots to code objects.
    Update PyCode_New() to take freevars and cellvars as arguments
Include/funcobject.h
    Add func_closure slot to function objects.
    Add GetClosure()/SetClosure() functions (and corresponding
    macros) for getting at the closure.
Include/frameobject.h
    PyFrame_New() now takes a closure.
Include/opcode.h
    Add four new opcodes: MAKE_CLOSURE, LOAD_CLOSURE, LOAD_DEREF,
    STORE_DEREF.
    Remove comment about old requirement for opcodes to fit in 7
    bits.
compile.c
    Implement changes to code objects for co_freevars and co_cellvars.

    Modify symbol table to use st_cur_name (string object for the name
    of the current scope) and st_cur_children (list of nested blocks).
    Also define st_nested, which might more properly be called
    st_cur_nested.  Add several DEF_XXX flags to track def-use
    information for free variables.

    New or modified functions of note:
    com_make_closure(struct compiling *, PyCodeObject *)
        Emit LOAD_CLOSURE opcodes as needed to pass cells for free
        variables into nested scope.
    com_addop_varname(struct compiling *, int, char *)
        Emits opcodes for LOAD_DEREF and STORE_DEREF.
    get_ref_type(struct compiling *, char *name)
        Return NAME_CLOSURE if ref type is FREE or CELL
    symtable_load_symbols(struct compiling *)
        Decides what variables are cell or free based on def-use info.
        Can now raise SyntaxError if nested scopes are mixed with
        exec or from blah import *.
    make_scope_info(PyObject *, PyObject *, int, int)
        Helper functions for symtable scope stack.
    symtable_update_free_vars(struct symtable *)
        After a code block has been analyzed, it must check each of
        its children for free variables that are not defined in the
        block.  If a variable is free in a child and not defined in
        the parent, then it is defined by block the enclosing the
        current one or it is a global.  This does the right logic.
    symtable_add_use() is now a macro for symtable_add_def()
    symtable_assign(struct symtable *, node *)
        Use goto instead of for (;;)

    Fixed bug in symtable where name of keyword argument in function
    call was treated as assignment in the scope of the call site. Ex:
        def f():
            g(a=2) # a was considered a local of f

ceval.c
    eval_code2() now take one more argument, a closure.
    Implement LOAD_CLOSURE, LOAD_DEREF, STORE_DEREF, MAKE_CLOSURE>

    Also: When name error occurs for global variable, report that the
    name was global in the error mesage.

Objects/frameobject.c
    Initialize f_closure to be a tuple containing space for cellvars
    and freevars.  f_closure is NULL if neither are present.
Objects/funcobject.c
    Add support for func_closure.
Python/import.c
    Change the magic number.
Python/marshal.c
    Track changes to code objects.

Closes SF patch #103123.

funcobject.h:

    PyFunctionObject: add the func_dict slot.

funcobject.c:

    PyFunction_New(): Initialize the func_dict slot to NULL.

    func_getattr(): Rename to func_getattro() and change the
    signature.  It's more efficient to use attro methods and dig the C
    string out than it is to re-convert a C string to a PyString.

    Also, add support for getting the __dict__ (a.k.a. func_dict)
    attribute, and for getting an arbitrary function attribute.

    func_setattr(): Rename to func_setattro() and change the signature
    for the same reason.  Also add support for setting __dict__
    (a.k.a. func_dict) and any arbitrary function attribute.

    func_dealloc(): Be sure to DECREF the func_dict slot.

    func_traverse(): Be sure to traverse func_dict too.

    PyFunction_Type: make the necessary func_?etattro() changes.

classobject.c:

    instancemethod_memberlist: Add __dict__

    instancemethod_setattro(): New method to set arbitrary attributes
    on methods (really the underlying im_func).  Raise TypeError when
    the instance is bound or when you're trying to set one of the
    reserved im_* attributes.

    instancemethod_getattr(): Renamed to instancemethod_getattro()
    since that's what it really is.  Also, added support fo getting
    arbitrary attributes through the im_func.

    PyMethod_Type: Do the ?etattr{,o} dance.

This should match the situation in the 1.6b1 tree.