Add better handling for IncludedModule to vm debug method
Add spec for calling super from toplevel module
Add spec for prepending into existing module chain
Add specs on Kernel#eval with local variables in the same binding.
Improve spec for prepending multiple modules by going through chain
Fix lookup start for super calls when prepending
Tag failing prepend specs for now
Rework Module#prepend and origin logic

This switches to a different mechanism to fix some issues with
Module#prepend exposed by previously added specs.

The problem was mostly wrong ordering and prepending into already
included modules into other classes. The first problem was solved by
actually using append logic for the additional modules that can be
included by a prepend.

Before all the modules from the prepended module were prepending,
resulting in a wrong ordering.

The redefinition problem is solved by making origin just a marked for
redefinition if it's different. This results in lookup logic to skip
that class / module that has a different origin and encounter it later
because it was readded as an included module later.
Remove tags for now passing specs
Use inline definition of lookup_begin now

This now has the same implementation as direct_class, but having a
separate method allows for easily changing this in the future if we need
different lookup starts from the actual class.
Merge pull request #2492 from razielgn/eval-fail-spec

Add specs on Kernel#eval with unreached locals across the same binding.
Return immediately on invalid character

Fixes #2458
Only clear fields when object allocation succeeds

This makes sure we get a no memory exception when we exhaust memory.

Fixes #2498
Small cleanup of source

Removes some unused stuff and marks appropriate stuff as const.
Use unsigned values consistently in Immix setup

Also makes sure the mask is a uintptr_t type so we always mask with a
defined behavior.
Fix compile error on newer GCC versions
Fix VM tests for changed type
More signedness attempts oh GCC 4.7
Add 2.0 versions for these language specs
Add specs for pattern matching with splats and post args