On some platform (OS X), llvm needs macros like
__STDC_LIMIT_MACROS defined in order to work, which is
normally defined in llvm-config. This patch modifies
the config to use CFG_LLVM_ROOT's llvm-config if it
exists, which fixes the compile failures.

This depends on llvm's 131294.

After all that, give up on "complex" version of type_has_pointers and just manually inspect. Can't calculate property during interning.

Move the ty_item_table into ty::ctxt.items, move variant_info to ty, and start sketching the contains_pointer property on types.

rustc: Unify variables using a single type instead of keeping a list and doing it all at the end. This will give us better error messages.

And fix a the single screw-up in the source code it caught.

No functional change. Largely removed the native module/non-native module distinction from resolve.rs

and kill dead code.

and various other tidying in typestate

Added visit_fn_pre and visit_fn_post fields that get applied to
both regular functions and methods.

This required quite a bit of tiresome plumbing about of spans.
On the bright side, now other errors can be converted to span_err too.

Includes test cases.

Started by rewriting collect_locals to use walk instead of fold

(Also, feel free to start adding logging to your code. Really. It's fast.)