Add Win64 calling convention.
Use the correct calling convention for extern rust functions.
Don't use win64 calling convention on 32-bit machines.
add an initial `Gc<T>` stub with the API
Make BytePos 32-bit
Fix parsing tests
auto merge of #10527 : eholk/rust/win64, r=alexcrichton

This was needed to access UEFI boot services in my new Boot2Rust experiment.

I also realized that Rust functions declared as extern always use the C calling convention regardless of how they were declared, so this pull request fixes that as well.
auto merge of #10576 : thestinger/rust/gc, r=pcwalton

This isn't very useful yet, but it does replace most functionality of `@T`. The `Mut<T>` type will make it unnecessary to have a `GcMut<T>` so I haven't included one. Obviously it doesn't work for trait objects but that needs to be figured out for `Rc<T>` too.
Fix --local-rust-root option on Windows
update manual to reflect &'lifetime syntax
auto merge of #10585 : idupree/rust/master, r=catamorphism
auto merge of #10567 : sanxiyn/rust/bytepos, r=alexcrichton
Remove ty_mac
auto merge of #10590 : sanxiyn/rust/ty-mac, r=thestinger
auto merge of #10584 : klutzy/rust/local-rust-root, r=alexcrichton

Fixes #8756.
remove segmented stacks from the manual
auto merge of #10587 : thestinger/rust/stack, r=pcwalton
`std::ptr::read_ptr` now takes `*T` instead of `*mut T`

Closes #10579
auto merge of #10595 : hatahet/rust/master, r=thestinger

Closes #10579
Process ffi generics in rustdoc

This prevents an assertion from being tripped because the generics weren't
categorized.

Closes #10597