This commit uniforms the short title of modules provided by libstd,
in order to make their roles more explicit when glancing at the index.
Signed-off-by: NLuca Bruno <lucab@debian.org>

Also remove all instances of 'self within the codebase.

This fixes #10889.

Closes #10240

It is simply defined as `f64` across every platform right now.

A use case hasn't been presented for a `float` type defined as the
highest precision floating point type implemented in hardware on the
platform. Performance-wise, using the smallest precision correct for the
use case greatly saves on cache space and allows for fitting more
numbers into SSE/AVX registers.

If there was a use case, this could be implemented as simply a type
alias or a struct thanks to `#[cfg(...)]`.

Closes #6592

The mailing list thread, for reference:

https://mail.mozilla.org/pipermail/rust-dev/2013-July/004632.html

Implement Clone and DeepClone for functions with 0 to 8 arguments.

This makes custom borrowing implementations for custom smart pointers
sound.

@T and @mut T for T: Const have DeepClone

Adds documentation for various things that I understand.
Adds #[allow(missing_doc)] for lots of things that I don't understand.

This only changes the directory names; it does not change the "real"
metadata names.

for deep copies through shared ownership boundaries

Performing a deep copy isn't ever desired for a persistent data
structure, and it requires a more complex implementation to do
correctly. A deep copy needs to check for cycles to avoid an infinite
loop.

The borrowck-borrow-from-expr-block test had to be updated. I'm not sure why
it compiled before since ~int was already clonable.

Also inlining some functions which take functions as arguments.