mk: Fix formatting of docs.mk
doc: Update style of index, organization and trim out some excess.
Add Pointer tutorial, rename borrowed pointer tutorial.
doc: Fix tests in pointer guide
std::rt: require known stack bounds for all tasks.

We just approximate with a 1 or 2 MB stack for native::start.
Remove trailing whitespace
Make CFG_LIBDIR configurable. Fixes #5223
auto merge of #11045 : jhasse/rust/patch-libdir, r=alexcrichton

See https://github.com/mozilla/rust/issues/5223#issuecomment-30455086
auto merge of #11364 : brson/rust/docs, r=alexcrichton

This reorganizes the documentation index to be more focused on the in-tree docs, and to clean up the style, and it also adds @steveklabnik's pointer guide.
Renamed Option::map_default and mutate_default to map_or and mutate_or_set
Remove unnecessary substitution of type params when generating
vtable methods before translating the ref to the method itself.
libextra: Introduce typed arenas.

A typed arena is a type of arena that can only allocate objects of one
type. It is 3x faster than the existing arena and 13x faster than malloc
on Mac.
librustc: Move block contexts into per-function arenas, and
stack-allocate function contexts.
doc: Syntax highlight the cheatsheet
doc: Fix table format in cheatsheet
doc: Title guides consistently
mk: Start testing the cheatsheet
doc: Highlight the testing guide correctly
mk: Fix the naming of the windows installer harder

CFG_VERSION includes a bunch of VCS info in it that is not a valid
filename. CFG_RELEASE is just the version number.
Fixed Gc::clone, implemented Gc::ptr_eq