Note that the method foo.each() is not de-moded, nor the other
vec routines.

Most could use the each method, but because of the hack used to
disambiguate old- and new-style loops, some had to use vec::each.

(This hack will go away soon.)

Issue #1619

This changes the indexing syntax from .() to [], the vector syntax from ~[] to
[] and the extension syntax from #fmt() to #fmt[]

I tried to pay attention to what was actually being tested so, e.g. when I
test was just using a vec as a boxed thing, I converted to boxed ints, etc.

Haven't converted the macro tests yet. Not sure what to do there.

This reverts commit d08b443f.

This reverts commit aa25f22f. It broke stage2, not sure why yet.

This giant commit changes the syntax of Rust to use "assert" for
"check" expressions that didn't mean anything to the typestate
system, and continue using "check" for checks that are used as
part of typestate checking.

Most of the changes are just replacing "check" with "assert" in test
cases and rustc.

Testing proper cleanup is hampered by
https://github.com/graydon/rust/issues/293