Should probably reorganize/rename the "lib_python" directory at some point.

Somehow had gotten the C API definitions of True and False backwards...

This is so that we can add the CAPI slots for things like tp_as_sequence,
so that C extensions will work properly.

I don't think there are very many extensions that would do this but let's
still support it for now; it further bloats the type objects but only as
much as it does in CPython as well.

Previously had hardcoded three different iterations.

- Start moving towards slotdefs
- add tp_repr support
- add an slots_tester extension module so we can test these more narrowly

Move some type-related stuff into typeobject.cpp or descrobject.cpp

Separated out from some more involved changes that are
required to get the 'pwd' module working.

Haven't added structseq.c to the build quite yet

Remove some definitions that should no longer be in there
(structs for which we have Pyston-internal definitions).

Instead of doing "typedef void PyIntObject", do
"struct _PyIntObject; typedef struct _PyIntObject PyIntObject;"
which prevents spurious things like type conversions or
sizeof(void)'s.

I'm not sure that we need to do this at the expression-level --
I think we just have to do it at the statement level.

ie 'from a import b' now attempts an 'import a.b' if b does not already exist.
This also works for imports caused by__all__.

Previously we were calling it just 'b'.

ScopeInfo involves checking the whole function subtree to resolve
scoping references.  SourceInfo has information about the specific
function.  is_generator used to be in ScopeInfo, but accessing it
would require doing the full subtree analysis, which can be
unnecessary.

This lets us avoid analyzing function subtrees that are never entered.