Replace StrAllocating.into_owned() with .into_string()

We already have into_string(), but it was implemented in terms of
into_owned(). Flip it around and deprecate into_owned().

Remove a few spurious calls to .into_owned() that existed in libregex
and librustdoc.
remove /build from .gitignore since there is build/
Revert erroneous fix to tutorial
syntax: Fix span on illegal ABI errors

Fixes #8537
Fixes #14499
Change to_owned() to to_string().
Make Arc::make_unique check weak refs; add make_unique to Rc

This patch makes `Arc::make_unique` examine the number of weak
references as well as strong references, which is required for safety.

It also adds a `make_unique` method to the `Rc` type for consistency.

Closes #14521.
auto merge of #14510 : kballard/rust/rename_strallocating_into_owned, r=alexcrichton

We already have into_string(), but it was implemented in terms of
into_owned(). Flip it around and deprecate into_owned().

Remove a few spurious calls to .into_owned() that existed in libregex
and librustdoc.
auto merge of #14512 : Heather/rust/patch-1, r=alexcrichton
Implement Show for Bitv{,Set}

Closes #14531
Rename OSRng to OsRng

According to Rust's style guide acronyms in type names should be
CamelCase.

[breaking-change]
Fix the handling of assignments to owning pointer paths in check_loans

Make check_for_assignment_to_restricted_or_frozen_location treat
mutation through an owning pointer the same way it treats mutation
through an &mut pointer, where mutability must be inherited from the
base path.

I also included GC pointers in this check, as that is what the
corresponding code in gather_loans/restrictions.rs does, but I don't
think there is a way to test this with the current language.

Fixes #14498.
auto merge of #14511 : Sawyer47/rust/osrng-rename, r=alexcrichton

According to Rust's style guide acronyms in type names should be
CamelCase.

[breaking-change]
auto merge of #14514 : Randati/rust/patch-1, r=huonw
auto merge of #14517 : lucy/rust/issue-14499, r=alexcrichton

Fixes #8537
Fixes #14499 (duplicate of #8537)

Old:
```rust
test.rs:2 	pub extern "xxxxx" fn add(x: int, y: int) -> int {
          	                   ^~
```

New:
```rust
test.rs:2 	pub extern "xxxxx" fn add(x: int, y: int) -> int {
          	           ^~~~~~~
```
auto merge of #14522 : aturon/rust/make_unique, r=alexcrichton,alexcrichton,me

This patch makes `Arc::make_unique` examine the number of weak
references as well as strong references, which is required for safety.

It also adds a `make_unique` method to the `Rc` type for consistency.

Closes #14521.
auto merge of #14524 : ahmedcharles/rust/to_string, r=alexcrichton
auto merge of #14535 : sfackler/rust/bitv-show, r=alexcrichton

Closes #14531
rustc: Add lint for snake_case functions & methods.
libsyntax: Fix snake_case errors.

A number of functions/methods have been moved or renamed to align
better with rust standard conventions.

syntax::ext::mtwt::xorPush => xor_push
syntax::parse::parser::Parser => Parser::new

[breaking-change]
lib{std,core,debug,rustuv,collections,native,regex}: Fix snake_case errors.

A number of functions/methods have been moved or renamed to align
better with rust standard conventions.

std::reflect::MovePtrAdaptor => MovePtrAdaptor::new
debug::reflect::MovePtrAdaptor => MovePtrAdaptor::new
std::repr::ReprVisitor => ReprVisitor::new
debug::repr::ReprVisitor => ReprVisitor::new
rustuv::homing::HomingIO.go_to_IO_home => go_to_io_home

[breaking-change]