In Pyston the PyCodeObject just an opaque pointer. Which can't calculate
the number of freevars. Implement a function to check whether there has
freevars in BoxedCode object.

add prefix to Pyston defined True and False

download cython from github instead of cython.org

cython.org is currently down

The current pyport.h missed somethings due to it started with an empty pyport.h. And add things
increfmentally from CPython, now copied all things in CPython pyport.h.

bool is technically a subclass of int. Revert that Pyston change to support some extensions.

Some extension will use `True` and `False` from other package. For
example, X11 defined `True` and `False` in `/usr/include/X11/Xlib.h`.
Which will cause name conflict when try to build extension with pygame.

For now, I think add a prefix to these is a acceptable sulotion.

And also use Py_True and Py_False as much as possible.

make more list unit test pass

Improve REPL support

This fixes a bug with expressions inside loops in interactive mode
that resulted in expressions not being printed:

    >> for i in range(3):
    ...    i
    ...
    >>

Python prints the value every iteration:

    >> for i in range(3):
    ...    i
    ...
    0
    1
    2
    >>>

The same also applies to while loops.

vregs: reuse block local vregs

user visible: used for all non compiler generated names, name could be used in a single block or multiple
              all frames contain atleast this vregs in order to do frame introspection
cross block : used for compiler generated names which get used in several blocks or which have closure scope
single block: used by compiler created names which are only used in a single block.
              get reused for different names

we assign the lowest numbers to the user visible ones, followed by the cross block ones and finally the single block
ones. we do this because not all tiers use all of the vregs and it still makes it fast to switch between tiers.

Fix some issues that crop up on 15.10

not very happy about this but it's better than having a flaky CI...

Some fixings that let scipy tests pass.

major bjit improvements

float.cpp: now that we have float.c use some of the functions directly

CPython has this check. I think Pyston missed it when switch to the
CPython way of handling some inheritance functionality.

References:
CPython code:
https://github.com/python/cpython/blob/2.7/Objects/typeobject.c#L4074
Pyston commit that switch to the CPython way of handling it:
https://github.com/dropbox/pyston/commit/251f417abd68c4b018217ae3b1901b3f1687384d#diff-a5cc3ff8c761716ba33b328ad1d042dfR1499

And also add an extension for test.

complexTruediv will pass subtype of float to complexDivFloat,
so loose the type check in complexDivFloat, use PyFloat_Check
instead check the type exactly.

For some struct member in Pyston itself, add `const` qualifier,
for exenstion, do not add `const` for compatibility reason.

Pyston's PyInt_AsLong implementation didn't check tp_as_number->nb_int,
use CPython implementation with some Pyston modifications to avoid
recursive call.

I think LLVM-tier compilation times got worse with refcounting,
which is why we've seen these tests time out more often lately.

this also workarounds the problem we were having on ubuntu 16.04 where we have to use std::isinf instead of isinf()

also add a option to pass MAP_32BIT to mmap

also fix a build error when ICs are disabled

I am not exactly sure why this ends up failing, but on my 15.10
machine I get the SSLv3 protocol but it ends up failing when the
test tries to connect.

CPython made this change, so copy it.

Temporarily disable the clang build on travis-CI