doc: Modernize FAQs just slightly
make: update dist target for renamed files

src/README.txt has been renamed in a30d61b05a, make dist is
thus failing as unable to find it.
This commit makes the dist target working again.

Signed-off-by: Luca Bruno <lucab@debian.org>
make: update dist target after libextra split

libextra is currently being split into several crates. This commit adds
them all to the dist target in order to have them in the final tarballs.

Signed-off-by: Luca Bruno <lucab@debian.org>
auto merge of #12112 : lucab/rust/make-dist, r=alexcrichton

`make dist` or building from a generated tarball is currently not possible due to some files that have been renamed and the ongoing libextra split. This PR fixes all (current) issues in order to build rust from the .tar.gz source alone.
Remove unused ConstMutability
Make &mut borrows restrict aliasing

Fixes #11913
Update deriving to pass around the `cx` linearly
extra::test: add an opaque function to assist with accurate
benchmarking.

This allows a result to be marked as "used" by passing it to a function
LLVM cannot see inside. By making `iter` generic and using this
`black_box` on the result benchmarks can get this behaviour simply by
returning their computation.
arena: use the generic `bh.iter` to stop the benchmarks being DCE'd.

Before:

    test test::bench_nonpod_nonarena  ... bench:        62 ns/iter (+/- 6)
    test test::bench_pod_nonarena     ... bench:         0 ns/iter (+/- 0)

After:

    test test::bench_nonpod_nonarena  ... bench:       158 ns/iter (+/- 11)
    test test::bench_pod_nonarena     ... bench:        48 ns/iter (+/- 2)

The other tests show no change, but are adjusted to use the generic
return value of `.iter` anyway so that this doesn't change in future.
Fix infinite loop in MemReader::read_until.
Fix infinite loop in BufReader::read_until.
auto merge of #12105 : huonw/rust/bench-black-box, r=alexcrichton

This allows a result to be marked as "used" by passing it to a function
LLVM cannot see inside (unless LTO is enabled).

Closes #8261.
auto merge of #12114 : brson/rust/faqs, r=cmr

These are ancient. I removed a bunch of questions that are less relevant - or completely unrelevant, updated other entries, and removed things that are already better expressed elsewhere.
Expand the testing guide to cover optimizations, benchmarks and how to
be more precise about what's being benchmarked.

Also, reorganise the layout a bit, to put examples directly in their
sections.
auto merge of #12106 : qpliu/rust/memreader-fill-eof, r=sfackler

I don't know if anything depends on MemReader::fill returning an empty slice instead of EndOfFile, but I'm pretty sure that MemReader::read_until should not go into an infinite loop.
Add new syntax extension fourcc!()

fourcc!() allows you to embed FourCC (or OSType) values that are
evaluated as u32 literals. It takes a 4-byte ASCII string and produces
the u32 resulting in interpreting those 4 bytes as a u32, using either
the platform-native endianness, or explicitly as big or little endian.
Converted fourcc! to loadable syntax extension
Default fourcc! to big-endian.

It was decided that a consistent result across platforms would be the
most useful and least surprising. A "target" option has been added to
get the old behaviour of using the target platform's endianess.
Allow codepoints 128-255 in fourc!!

Codepoints with those values will be interpreted as bytes with their
raw codepoint value. ('\xAB' -> 0xABu8, etc.) Codepoints > 255 remain
forbidden.
std::io: Add `Chars` iterator for Buffer.

Add `std::io::Chars` iterator and `Buffer#chars()` method