Fix: BigInt tests fail on 32-bit platforms
test: fix check-fast breakage.
librustc: Allow the type parameter version of `Self` to be spelled with a capital S
librustc: Implement `&static` as the replacement for `Durable`. r=nmatsakis
Merge pull request #4414 from gifnksm/bigint-test

Issue 4393 BigInt tests fail on 32-bit platforms
mode: reset mode on entry to fn body.

This is an interim fix to address the "Beware!" unsoundness.  I have a
more comprehensive rewrite of mode.rs in the pipeline.

r=pcwalton
tests: Add two test cases, one xfailed
correct expected error msgs in various tests rs=breakage
Add test cases: one xfailed, one not
Add working test for issue 3935 and xfailed test for issue 3888