Introduce VecPerParamSpace and use it to represent sets of types and
parameters

This involves numerous substeps:

1. Treat Self same as any other parameter.
2. No longer compute offsets for method parameters.
3. Store all generic types (both trait/impl and method) with a method,
   eliminating odd discrepancies.
4. Stop doing unspeakable things to static methods and instead just use
   the natural types, now that we can easily add the type parameters from
   trait into the method's polytype.
5. No doubt some more. It was hard to separate these into distinct commits.

Fixes #13564
auto merge of #14604 : nikomatsakis/rust/issue-5527-namespace-substs, r=pcwalton

The current setup is to have a single vector of type parameters in
scope at any one time. We then have to concatenate the parameters from
the impl/trait with those of the method. This makes a lot of things
awkward, most notably associated fns ("static fns"). This branch
restructures the substitutions into three distinct namespaces (type,
self, fn). This makes most of the "type parameter management"
trivial. This also sets us up to support UFCS (though I haven't made
any particular changes in that direction in this patch).

Along the way, this patch fixes a few miscellaneous bits of code cleanup:

1. Patch resolve to detect references to out-of-scope type parameters,
   rather than checking for "out of bound" indices during substitution
   (fixes #14603).

2. Move def out of libsyntax into librustc where it belongs. I should have
   moved DefId too, but didn't.
   
3. Permit homogeneous tuples like `(T, T, T)` to be used as fixed-length
   vectors like `[T, ..3]`. This is awfully handy, though public facing.
   I suppose it requires an RFC.

4. Add some missing tests.

cc #5527

r? @pcwalton or @pnkfelix
librustc: Fix the issue with labels shadowing variable names by making
the leading quote part of the identifier for the purposes of hygiene.

This adopts @jbclements' solution to #14539.

I'm not sure if this is a breaking change or not.

Closes #12512.

[breaking-change]
Improve error messages for io::fs
std: Rebase better errors on master
libsyntax: Allow `+` to separate trait bounds from objects.

RFC #27.

After a snapshot, the old syntax will be removed.

This can break some code that looked like `foo as &Trait:Send`. Now you
will need to write `foo as (&Trait+Send)`.

Closes #12778.

[breaking-change]
configure: Don't sync unused submodules

If the compiler is built with --{llvm,jemalloc,libuv}-root, then the configure
script can skip updating these submodules.

Closes #14822
Remove typo on collections::treemap::UnionItems

The docstring stated it was a intersection iterator, when in fact it is the union iterator
Fix the unused struct field lint for struct variants

Fixes #14837.
Clarify `Any` docs

The `Any` docs previously did not state that only `'static` types implement it.
rustc: [T, ..N] and [T, ..N+1] are not the same

This commit fixes a bug in the calculation of the hash of a type which didn't
factor in the length of a constant-sized vector. As a result of this, a type
placed into an Any of a fixed length could be peeled out with any other fixed
length in a safe manner.
Audit usage of NativeMutex

Once a native mutex has been used once, it is never allowed to be moved again.
This is because some pthreads implementations take pointers inside the mutex
itself.

This commit adds stern wording around the methods on native mutexes, and fixes
one use case in the codebase. The Mutex type in libsync was susceptible to
movement, so the inner static mutex is now boxed to ensure that the address of
the native mutex is constant.
remove unnecessary PaX detection

Rust no longer has support for JIT compilation, so it doesn't currently
require a PaX MPROTECT exception. The extended attributes are preferred
over modifying the binaries so it's not actually going to work on most
systems like this anyway.

If JIT compilation ends up being supported again, it should handle this
by *always* applying the exception via an extended attribute without
performing auto-detection of PaX on the host. The `paxctl` tool is only
necessary with the older method involving modifying the ELF binary.
librustc: Take in account mutability when casting array to raw ptr.
librustc: Forbid `transmute` from being called on types whose size is
only known post-monomorphization, and report `transmute` errors before
the code is generated for that `transmute`.

This can break code that looked like:

    unsafe fn f<T>(x: T) {
        let y: int = transmute(x);
    }

Change such code to take a type parameter that has the same size as the
type being transmuted to.

Closes #12898.

[breaking-change]
syntax: fix quote_pat! & unignore a quotation test.
syntax: parse outer attributes in `quote_item!` calls.

Fixes #14857.
Rolling up PRs in the queue

Closes #14797 (librustc: Fix the issue with labels shadowing variable names by making)
Closes #14823 (Improve error messages for io::fs)
Closes #14827 (libsyntax: Allow `+` to separate trait bounds from objects.)
Closes #14834 (configure: Don't sync unused submodules)
Closes #14838 (Remove typo on collections::treemap::UnionItems)
Closes #14839 (Fix the unused struct field lint for struct variants)
Closes #14840 (Clarify `Any` docs)
Closes #14846 (rustc: [T, ..N] and [T, ..N+1] are not the same)
Closes #14847 (Audit usage of NativeMutex)
Closes #14850 (remove unnecessary PaX detection)
Closes #14856 (librustc: Take in account mutability when casting array to raw ptr.)
Closes #14859 (librustc: Forbid `transmute` from being called on types whose size is)
Closes #14860 (Fix `quote_pat!` & parse outer attributes in `quote_item!`)