Improved the search by including a levenshtein distance calculation which enables the docs search function to be more forgiving for spelling mistakes
Updated the licensing information for the Levenshtein distance function
Change Shl<T, T> for Int to Shl<uint, T>
doc/guide-ffi: A few minor typo/language fixes

Signed-off-by: Anton Lofgren <alofgren@op5.com>
Relicense shootout-threadring.rs

Everyone agreed.

Related to #14248, close #15328
Add example for str replace() and MaybeOwned

  - for 3 implementations of into_maybe_owned()
  - is_slice()
  - is_owned()
Define a new setting g:rust_fold

g:rust_fold allows folding to be enabled. This lets the user turn on
folding without having to define autocommands.
Set softtabstop, textwidth, and optionally colorcolumn

Setting softtabstop makes <Del> delete 4 spaces as if it were a tab.

Setting textwidth allows comments to be wrapped automatically. It's set
at 80, which is the recommended line length for Rust programs. There are
suggestions that it should be 79, but our current style guide says 80 so
that's what we're matching.

A new setting g:rust_colorcolumn sets colorcolumn as well, to +1,101.
This indicates both the textwidth and the second stricter line length of
100 that our style guide lists.
Remove rust_colorcolumn, set textwidth to 99

The latest change to aturon/rust-guidelines states that lines must not
exceed 99 characters. This gets rid of the 80/100 split, so we don't
need to customize colorcolumn amymore.
Guide: match
Guide: looping
Guide: Standard input
rustc: Always mark #[crate_name] as used

It's just an annoying error if you use --crate-name on the command line and you
also have a #[crate_name] specified
rustc: Exclude #[repr(C)] from non camel case

C structs predominately do not use camel case identifiers, and we have a clear
indicator for what's a C struct now, so excuse all of them from this stylistic
lint.
Some documentation fixes and improvements
install: Make the LD_LIRARY_PATH warning more aesthetic
install: Run ldconfig when installing on Unix. Closes #15596.

If ldconfig fails it emits a warning. This is very possible when installing
to a non-system directory, so the warning tries to indicate that it may
not be a problem.
webfonts: name fix
rustdoc: Change type name of raw pointer from *T to *const T

Update the formatting of raw immutable pointers to print *const T.
Allow writes of length 0 to a full buffer