support 'linux2', 'darwin', and 'unknown' for sys.platform

Conflicts:
	src/runtime/builtin_modules/builtins.cpp
	src/runtime/import.cpp

split cmake_check to cmake_check and clang_check

Fix a couple misc issues along the way

The callers were assuming that the module represents the globals,
which is not always true.

We can currently fetch globals from the interpreter, but not the jit.
We don't allow custom globals through the jit, so for now we can just
return the module; I think we should be able to support the jit by adding
the globals as a stackmap arg.

We should be able to support them in the JIT, but do the easy thing
for now.

also, put the globals info on the ScopingAnalysis instead of ScopeInfo

All the old prints still exist, but at -vv or even -vvv mode.

The basic system is:
-v mode gives information about the overall execution: what functions we
    run into, what things take longer than we expected, etc.
-vv mode gives information about each function: the cfg, llvm ir, etc.
-vvv gives information about each BB.

cmake configure script

-add sizeof(pyston::BoxedDict) to config.h

use a binary search to find/insert CompiledFunction*'s into the registry

colocate string and tuple data

Tuples now contain a pointer to their storage (Box**) + size, and strings contain
an llvm::StringRef which contains the pointer+size.

use the same hash function for both unicode and string objects

this keeps us from having to utf8 decode unicode objects (into BoxedStrings)
whenever we want to hash them.

free generator stacks both in the destructor and when a generator exits.

we're already unmapping the redzone as part of the munmap() call.  also, free the generator stack from the sending side, not from within the generator.

a few changes which help out GC performance

when looking up a child hidden class we look up the attr in the child_index map,
then get the HiddenClass* from the children vector (at that index.)

this speeds up GC substantially by letting us visit the range from the vector as
opposed to iterating through the stringmap.

add a map-like container that keeps its values contiguous so we can use the efficient gc_visitor->visitRange.

also, don't register MAX_STACK_SIZE bytes with the GC, register INITIAL_STACK_SIZE.

Somewhat tricky since it assumes __dict__ is always a dict object;
I think I caught most of the places though.

implemented kmod's suggestions

through syntax error when you to `del` a var stored in a closure

add option to tester script to skip specified tests

Conflicts:
	src/codegen/ast_interpreter.cpp
	src/runtime/types.cpp

Update INSTALLING.md

add "sudo" before apt-get
It seems a typo?

add StackRoot<> and #defines for DECREF