rustc: Get LLVM error message safely

On Windows, `LLVMRustGetLastError()` may return non-utf8 mojibake string
if system uses non-English locale. It caused ICE when llvm fails.
This patch doesn't fix the real problem, but just make rustc not die.
rustdoc: Don't escape contents of headers

Turns out sundown has already escaped this content for us, so there's no need
for us to escape it again.

Closes #12736
test: Add some tests for closed issues

Closes #6738
Closes #7061
Closes #7899
Closes #9719
Closes #10028
Closes #10228
Closes #10401
Closes #11192
Closes #11508
Closes #11529
Closes #11873
Closes #11925
auto merge of #12732 : klutzy/rust/this-is-windows, r=alexcrichton

On Windows, `LLVMRustGetLastError()` may return non-utf8 mojibake string
if system uses non-English locale. It caused ICE when llvm fails.
This patch doesn't fix the real problem, but just make rustc not die.
auto merge of #12737 : alexcrichton/rust/issue-12736, r=brson

Turns out sundown has already escaped this content for us, so there's no need
for us to escape it again.

Closes #12736
auto merge of #12738 : alexcrichton/rust/needstest, r=brson,just

Closes #6738
Closes #7061
Closes #7899
Closes #9719
Closes #10028
Closes #10228
Closes #10401
Closes #11192
Closes #11508
Closes #11529
Closes #11873
Closes #11925
rustc: Move to FNV hashing for node/def ids

This leverages the new hashing framework and hashmap implementation to provide a
much speedier hashing algorithm for node ids and def ids. The hash algorithm
used is currentl FNV hashing, but it's quite easy to swap out.

I originally implemented hashing as the identity function, but this actually
ended up in slowing down rustc compiling libstd from 8s to 13s. I would suspect
that this is a result of a large number of collisions.

With FNV hashing, we get these timings (compiling with --no-trans, in seconds):

|           |  before  |  after  |
|-----------|---------:|--------:|
| libstd    |   8.324  |  6.703  |
| stdtest   |  47.674  | 46.857  |
| libsyntax |   9.918  |  8.400  |
collections: Correct with_capacity_and_hasher

The arguments were accidentally swapped in the wrong order.

Closes #12743
syntax: Conditionally deriving(Hash) with Writers

If #[feature(default_type_parameters)] is enabled for a crate, then
deriving(Hash) will expand with Hash<W: Writer> instead of Hash<SipState> so
more hash algorithms can be used.
auto merge of #12635 : alexcrichton/rust/speedy-hash, r=brson

This leverages the new hashing framework and hashmap implementation to provide a
much speedier hashing algorithm for node ids and def ids. The hash algorithm
used is currentl FNV hashing, but it's quite easy to swap out.

I originally implemented hashing as the identity function, but this actually
ended up in slowing down rustc compiling libstd from 8s to 13s. I would suspect
that this is a result of a large number of collisions.

With FNV hashing, we get these timings (compiling with --no-trans, in seconds):

|           |  before  |  after  |
|-----------|---------:|--------:|
| libstd    |   8.324  |  6.703  |
| stdtest   |  47.674  | 46.857  |
| libsyntax |   9.918  |  8.400  |
auto merge of #12746 : alexcrichton/rust/issue-12743, r=brson

The arguments were accidentally swapped in the wrong order.

Closes #12743
std: stop `vec!()` warning about unused mutability.

If no arguments are given to `vec!` then no pushes are emitted and
so the compiler (rightly) complains that the mutability of `temp` is
never used.

This behaviour is rather annoying for users.
change FVN hash function to the FVN-1a variant
auto merge of #12749 : tedhorst/rust/master, r=huonw

Minor change to the FVN hashing function based on recommendation on: http://en.wikipedia.org/wiki/Fowler_Noll_Vo_hash

cc @alexcrichton
rename ast::ViewItemExternMod to ast::ViewItemExternCrate, and clean::ExternMod to clean::ExternCrate
auto merge of #12750 : liigo/rust/De-extern-mod, r=alexcrichton

rename ast::ViewItemExternMod to ast::ViewItemExternCrate
rename rustdoc::clean::ExternMod to rustdoc::clean::ExternCrate
because `extern mod` is out.
auto merge of #12753 : huonw/rust/vec-macro, r=cmr

If no arguments are given to `vec!` then no pushes are emitted and
so the compiler (rightly) complains that the mutability of `temp` is
never used.

This behaviour is rather annoying for users.
Refactored get_metadata_section to return a Result<T,~str> instead of a Option. This provides more clarity to the user through the debug output [--ls].