Rationals that have a 1 denom should print like ints
Simplify PatIdent to contain an Ident rather than a Path

Rationale: for what appear to be historical reasons only, the PatIdent contains
a Path rather than an Ident.  This means that there are many places in the code
where an ident is artificially promoted to a path, and---much more problematically---
a bunch of elements from a path are simply thrown away, which seems like an invitation
to some really nasty bugs.

This commit replaces the Path in a PatIdent with a SpannedIdent, which just contains an ident
and a span.
Guide: add mutable binding section

Fixes #15334.
Fix ICE with nested macro_rules!-style macros

Fixes #10536.
remove duplicated slash in install script path
correct a few spelling mistakes in the tutorial
librustc: Have the kind checker check sub-bounds in trait casts.

This can break code that looked like:

    struct S<T> {
        val: T,
    }
    trait Gettable<T> {
        ...
    }
    impl<T: Copy> Gettable<T> for S<T> {
        ...
    }
    let t: Box<S<String>> = box S {
        val: "one".to_string(),
    };
    let a = t as Box<Gettable<String>>;
    //                        ^ note no `Copy` bound

Change this code to:

    impl<T> Gettable<T> for S<T> {
    //   ^ remove `Copy` bound
        ...
    }

Closes #14061.

[breaking-change]
Fix spelling errors.
Rename set_broadast() to set_broadcast().
Simplify creating a parser from a token tree

Closes #15306
Add examples for StrVector methods

- examples for connect and concat
- also fixed extra word in existing docs
collections: grow should use the overflow-checked reserve_additional
collections: Fix conditional when reserving extra vec space
Fix minor issues in the documentation of libtime.

- When the timezone is UTC, the "zone" field of the RFC 822 format is
  "GMT" (or "UT"), not "UTC."

- Although the name of `rfc3999` refers to RFC 3999, the documentation
  of it refers only to ISO 8601. This commit adds a description of the
  relation between ISO 8601 and RFC 3999.

Signed-off-by: OGINO Masanori <masanori.ogino@gmail.com>
Test fixes from the rollup