and introduce more indirection where it may be needed

Add len to str extensions

Use node IDs rather than types to ensure exported names are unique.
duplicate symbol. Closes #2074.

In the tutorial, use the crate_type attribute when discussing crate files that
are libraries, and only refer to the --lib files when talking about making a
single source file into a library.

Closes #2070.

Because terr_record_mismatch was getting called by infer::flds,
which takes types a and b where it's trying to prove a <: b, the
expected and actual fields were switched. Fixed it. Closes #2094

This example got left out for some reason.

Closes #2120.

This will be used for stack crawling, which in turn will be used for GC and
unwinding.

- we now distinguish bound/free parameters (see region-param
  test case for why this is necessary)
- we also track bounds on region variables
- also, restructure fold_ty() to have multiple variants without
  duplication instead of one overloaded folder.  This also allows
  for using block functions.

Add an optional --logfile argument to std::test::test_main and to
compiletest.

Use this features and the new 'check-summary.py' script to
summarise all the tests performed by the 'check' target. This is
a short term fix for #2075.

fleshing out time.rs