Typeck: Disallow scalar casts to bare_fn.

Bare functions are another example of a scalar but non-numeric
type (like char) that should be handled separately in casts.
This disallows expressions like `0 as extern "Rust" fn() -> int;`.

It might be advantageous to allow casts between bare functions
and raw pointers in unsafe code in the future, to pass function
pointers between Rust and C.

Closes #8728
rustdoc: Strip methods correctly based on privacy

Beforehand the id of a method was the id of the 'self' argument, but this is not
the id which privacy was using (the id of the ast::method) struct, so by moving
the ids over to the privacy-target ones the methods are now stripped correctly.
Fix struct field visibility and add enum field doc

Struct fields with inherited visibility were previously stripped.

Closes #9899
Check unnecessary visibility for struct variants
remove rust and rusti from driver.rs
auto merge of #9941 : alexcrichton/rust/rustdoc, r=huonw

Beforehand the id of a method was the id of the 'self' argument, but this is not
the id which privacy was using (the id of the ast::method) struct, so by moving
the ids over to the privacy-target ones the methods are now stripped correctly.
auto merge of #9946 : sfackler/rust/enum-doc, r=alexcrichton

Struct fields with inherited visibility were previously stripped.

Closes #9899
std::fmt: fix markdown peculiarity, unicodify some arrows, ` some trait names.
Use __morestack to detect stack overflow

This commit resumes management of the stack boundaries and limits when switching
between tasks. This additionally leverages the __morestack function to run code
on "stack overflow". The current behavior is to abort the process, but this is
probably not the best behavior in the long term (for deails, see the comment I
wrote up in the stack exhaustion routine).
auto merge of #9834 : alexcrichton/rust/morestack, r=brson

This commit re-introduces the functionality of __morestack in a way that it was
not originally anticipated. Rust does not currently have segmented stacks,
rather just large stack segments. We do not detect when these stack segments are
overrun currently, but this commit leverages __morestack in order to check this.

This commit purges a lot of the old __morestack and stack limit C++
functionality, migrating the necessary chunks to rust. The stack limit is now
entirely maintained in rust, and the "main logic bits" of __morestack are now
also implemented in rust as well.

I put my best effort into validating that this currently builds and runs successfully on osx and linux 32/64 bit, but I was unable to get this working on windows. We never did have unwinding through __morestack frames, and although I tried poking at it for a bit, I was unable to understand why we don't get unwinding right now.

A focus of this commit is to implement as much of the logic in rust as possible. This involved some liberal usage of `no_split_stack` in various locations, along with some use of the `asm!` macro (scary). I modified a bit of C++ to stop calling `record_sp_limit` because this is no longer defined in C++, rather in rust.

Another consequence of this commit is that `thread_local_storage::{get, set}` must both be flagged with `#[rust_stack]`. I've briefly looked at the implementations on osx/linux/windows to ensure that they're pretty small stacks, and I'm pretty sure that they're definitely less than 20K stacks, so we probably don't have a lot to worry about.

Other things worthy of note:
* The default stack size is now 4MB instead of 2MB. This is so that when we request 2MB to call a C function you don't immediately overflow because you have consumed any stack at all.
* `asm!` is actually pretty cool, maybe we could actually define context switching with it?
* I wanted to add links to the internet about all this jazz of storing information in TLS, but I was only able to find a link for the windows implementation. Otherwise my suggestion is just "disassemble on that arch and see what happens"
* I put my best effort forward on arm/mips to tweak __morestack correctly, we have no ability to test this so an extra set of eyes would be useful on these spots.
* This is all really tricky stuff, so I tried to put as many comments as I thought were necessary, but if anything is still unclear (or I completely forgot to take something into account), I'm willing to write more!
auto merge of #9949 : Heather/rust/driver-rs-cleanup-pullrequest, r=thestinger
doc: switch pandoc to html5
doc/rust.HTML: proper version box
auto merge of #9952 : huonw/rust/fmt-doc, r=alexcrichton

Cf. the concern raised in https://github.com/mozilla/rust/pull/9938#issuecomment-26648696.
auto merge of #9956 : sfackler/rust/more-more-visibility, r=alexcrichton
Fix unicode errors on Windows in path_is_dir, path_exists, getcwd and rust_localtime.

This make these functions use wchar_t version of APIs, instead of char version.
testsuite: test for fixed issue. Closes #7580.

Fixed by the privacy changes that allowed the `mod std {}` at the top
level of `std` to be non-`pub`.
auto merge of #9973 : huonw/rust/7580, r=luqmana

Fixed by the privacy changes that allowed the `mod std {}` at the top
level of `std` to be non-`pub`.
auto merge of #9812 : HNO3/rust/windows-utf8, r=alexcrichton

This fixes #9418 and #9618, and potential problems related to directory walking.
fix typo