Some improvements to the Cargo compiler file.
Use rustc's errorformat and add option to specify permanent parameters.
Updates based on kballard's feedback.
Added check for absolute file path, removed hard tab, and added documentation for new option.
rust-mode.el: Tweak syntax table

"_" should keep the default syntax class (symbol, not word). This
allows, e.g., `forward-word' to behave in the familiar way, jumping to
underscores within a function or variable name.
removed struct_variant feature from tests
Update the Vim syntax prelude.
fixed markdown rendering a H1 in comment
test/run-make: some test cases lacked $(EXTRACFLAGS).

Signed-off-by: NODA, Kai <nodakai@gmail.com>
Removed unneeded conversion to a slice.

Vec<T> can index now so its a useless conversion.
doc: adding example for type definitions
Add comment on why `RefCell::unwrap` is safe
Implement BorrowFrom<&'a T> for T (with mutable variants)
Mention that find() doesn't consume the full iterator
libs: make Cow usable, improve documentation

This commit makes `Cow` more usable by allowing it to be applied to
unsized types (as was intended) and providing some basic `ToOwned`
implementations on slice types. It also corrects the documentation for
`Cow` to no longer mention `DerefMut`, and adds an example.
Fix an ICE on diagnostics originating in external macros
mk/stage0: complain instead of creating an empty file

If the expected rustc snapshot is not where we expect it to be,
complain and fail at that point rather than creating a empty rustc file
and continuing until we try to run it.
mk/target: fix typo so we depend on the correct directory

Without this, if we we're using a non-standard host libdir, the target
bindir would not exist (and rustc would fail to write to the
non-existent directory).
rustdoc: avoid supplying a bad default sysroot so the librustc code can calculate it properly
configure: silence warning about LOCAL_RUST_ROOT being set

We have a default value for this ('/usr/local'), so this warning is
printed ALL the time unless one does --enable-local-rust. As a result,
it doesn't really help at all.