Some improvements to the Cargo compiler file.
Use rustc's errorformat and add option to specify permanent parameters.
Updates based on kballard's feedback.
Added check for absolute file path, removed hard tab, and added documentation for new option.
Fix `Vec::map_in_place` not doing what is written in the comment
libstd: improve os::args() doc
Guide: add a pointer to play.rust-lang.org and explain how to run the code examples.
Fix for issue #17574
Look for standard crates in LIBDIR provided by --libdir option,
not in hardcoded libdir path. If there was no LIBDIR provided
during configuration fallback to hardcoded paths.

Thanks to Jan Niklas Hasse for solution and to Alex Crichton for improvements.

Closes #11671
Conformed the 100 char limit and changed colon to semicolon
libsyntax: Add `parse_view_item` method to Parser
libsyntax: Add tests for `parse_view_item`
Reference: Add missing third dot of range
librustrt: check for mips+linux config in stack_overflow
Place parenthetical notation under the `unboxed_closure` feature-gate.
Consolidate the `unboxed_closure_sugar` and `unboxed_closure` feature gates.
Pull out the fn-sig sub/lub/glb code and generalize it into a `higher_ranked` module. Also moves the docs to a more suitable place.
Switch the code to use De Bruijn indices rather than binder-ids.
Introduce some sanity checking assertions in trans, erase regions more aggressively.
Make it an error to use parenthetical notation with
something other than a trait type.
Convert TyPolyTraitRef to accept arbitary bounds, so that things like
`Box<for<'a> Foo<&'a T> + 'a>` can be accepted. Also cleanup the visitor/fold
in general, exposing more callbacks.