mk/cfg: add .mk suffix on files to avoid "supprises" when backup files (file~) are in the directory
removed usage of struct_variant feature as it is no longer gated
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
Add -Z print-sysroot commandline option to rustc.
debuginfo: Add script that allows to conveniently start LLDB in "rust-mode"
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
Fix c_char on ARM

c_char is u8 on ARM

[breaking-change]
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.