Fix leak check after path changes

this check is not very robust :-(

Undo all the places we changed installed paths

The only things left in there were some old stubs.  We had added the stubs and then later
added the real files; with the old directory structure the real files took precedence,
but then with the new structure the stubs took precedence.

Once those were deleted there wasn't anything left in lib_pyston

We used to have a installed directory structure that mirrors
our source structure.  This required changing quite a few pieces of CPython
code to look in the new places (virtualenv, distutils, getpath.c, sysconfig).
So, undo all those changes, and change our CMake configuration to install into
the paths that CPython expects.

Note: "the paths that CPython expects" is platform-dependent.  The paths I added
here are based on the "posix" style that it supports.  The CPython code has platform-specific
code to look in different places, and I guess the build system must have platform-specific
knowledge of where to put it as well, but our CMake system will always put it in the linux variant.

Fix pointer reuse problems

while this removes some disabled features I'm not a big fan of having disabled stuff around
because it will break and makes development harder.

this is a duplicate - we will allready emit a call to recordType inside the bjit

solves a pointer reuse problem

Remove libpypa parser

After remove libpypa, the function getMagic only return one string. So
just use a char array constant instead a function.

MCJIT: free loaded objects

This fixes the llvm tier memory consumption until we migrate to the ORC JIT which has better memory management.

Misc memory size reductions

this does not hurt perf but still saves some memory

Threading fixes to get cffi-1.7 working

Instead of having it always point to the thread-local threadstate object,
it's a global that gets updated during context switches, like CPython does it.

There are still a number of differences that should be refactored out, but
I think this should bring us quite a bit closer to CPython's implementation.

It's time :(

This new version is causing some issues for us

switch from the SSE prefetch to __builtin_prefetch

string interning: make it slightly more space efficient

hidden classes: free classes of singleton type

this fixes the huge (~350MB) leak in:
for i in xrange(1000000):
    class C(object):
        pass

We used to store the string content twice.
This implementation makes use of DenseSet::find_as functionality where one can search using a different type.
I was not sure if the special DenseMapInfo I had to create causes any problems so I choose to create a new source file
for it so that it does not get picked up somewhere else.