use PyObject_Malloc in pyston::DenseMap, smaller ICInvalidator, reduce malloc calls

llvm::SmallPtrSet<ICSlotInfo*, 2> and std::unordered_set<ICSlotInfo*> have the same size
but the SmallPtrSet has the advantage that it can already store 2 elements in there and does not allocate 10 elements in the constructor

it is slighlty faster for small allocations and has the advantage that it is easier to track how much memory our python objects are using

runtime ICs: use mmap instead of malloc for executable code

don't handle functions containing lambdas with yields as generators

make inner links to dir format

I'm suprised we did not run into this earlier...

use more often std::unique_ptr

This stuff got mostly already manually freed but I think this change makes it a little easier to see who owns what.

we should not execute memory which got allocated using malloc
(crashes a lot of memory inspection tools and also the windows subsystem for linux)
I replaced it with a trivial mmap allocator which never unmaps the memory
(but reuses the memory if a runtime ICs gets deleted)
I think this is fine for now:
- there are <100 runtime ICs used per test
- because all runtime ICs have the same size there is no problem with fragmentation

ICSlotInfo: remove old invalidator entries

delete the llvm module after code generation

this saves a lot of memory

Switch to CPython list sort(Not its list implementation)

If BoxedList::allocated is -1, it means the items inside were changed.
Some CPython list functions need this to check exceptions.

CPython listsort need "allocated" to check and throw exception:
https://github.com/Daetalus/pyston/blob/d84105ffc8a4855bb6e00d9c22ba2baa8bddf969/from_cpython/Objects/listobject.c#L2091
https://github.com/Daetalus/pyston/blob/d84105ffc8a4855bb6e00d9c22ba2baa8bddf969/from_cpython/Objects/listobject.c#L2180

Comment out some part of listobject.c, use the CPython list sort and
apply some changes to existed Pyston code.

ScopeNameUsage merge dicts into a single big one

and change it to use a unordered_map because it uses less memory in this case and is faster
(I assume because it does not have align the key value tuples)
saves about 10% of peak memory on django

Update to fewer-pyston-changes virtualenv

hidden classes: split into subclasses to reduce memory consumption

+ use pyston::DenseMap to save a little more memory

this saves about 5%-10% of peak memory on django

Fix evaluation order for dict operations

enable `PyObject_Format` in `from_cpython/Objects/abstract.c`

using cpython's `sys.flags` inplementation

Support empty lines on the repl

They end up generating "pass" statements with a lineno of 0, which
trips an assert later on.  This commit just sets them to have a lineno
of 1.

I'm not sure how to test this, since piping into stdin is supposed to
be treated as a file (not as the repl).  Though, we get that wrong right now.