std::rt: require known stack bounds for all tasks.

We just approximate with a 1 or 2 MB stack for native::start.
Remove unnecessary substitution of type params when generating
vtable methods before translating the ref to the method itself.
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
doc: Title reference manual consistently
doc: Fix URL of libextra docs
'borrowed pointer' -> 'reference'
doc: Add libgreen and libnative to the index
doc: Add rustc and syntax to the index
Address some minor points in the pointer guide

cc #11364.
Fixed code snippets
doc: Typos
Fix leaking trait imports across modules

Turns out the pass in resolve was a little too eager to travel back up the
hierarchy chain when looking for trait candidates.

Closes #10465
rustc: De-indent portions of middle::resolve

It's a little prettier to look at now