Move our integration tests to a separate repository

By default it just does `git submodule init`

Enable future builtins module and add test file

Hash improvement for complex, str and long.

section ordering hack: use the PGO-determined ordering

Rather than do anything smart, just copy the ordering that the
pgo build used.  To keep the file reasonable, only emit
entries for functions that appear in the perf results (cuts from
>1M entries to ~2k).

I tried getting the hhvm "hfsort" to work, but ran into some
fixable-but-annoying issues getting it integrated (ex need to bring
in some other libraries).  Let's just try this for now; the goal
isn't to get the absolute best performance anyway, since for that
we'll use PGO and ignore the section ordering file.

getiter: use tp_iter for non python types

Some improvements to make test unary could pass

Recursive printing

Enable `test slice` and add missing function.

Haven't looked into it that much, but my guess is that it
was introduced in some newer version of clang than what
some people are using.  It was added for the use of the
clang-pgo build, but we ended up dropping that so it should
be ok to drop this flag.

Make Raise and Subscript exprs use capi exceptions

Add some function to old style class

And fix a bunch of resulting issues (mostly just some pretty benign
assertion errors).

Less helpful than I thought for now -- the KeyErrors are thrown
by a custom class that does `raise KeyError`, so we won't benefit
from this until we can have jitted code throw (not just receive)
capi exceptions.

Import the ctypes module.

Small bjit improvements + fixes the build

Add tip on how to debug infinite recursive bugs from tp_ slots.