Update documentation for from_raw_parts

Fixes #19269.
impl Clone for Cow
small doc fixes

We don't need this &mut, and vec could use []s
Add test for #18908
fix expand_quote_ty function as parse_ty was changed and needs no arguments now
Fix typo in reference.md
Allow trailing commas in array patterns and attributes
Simplify `RefCell` code a bit, make `deref` a no-op.
std: add tests for the Vec<u8> Writer impl
std: add Reader impl for &[u8]
rustdoc: Check for href when prepending rootPath

Fixes #18354.
better wording
replace 'but' with 'and'
Improve documentation of checked_* functions
Update comment to current file path for intrinsics
lldb: Fix pretty printer for nullable-opt enums with fat pointers.
gdb: Fix pretty printer for nullable-opt enums with fat pointers.
Fixed out of date comment on `copy_memory`
libtest: get rid of dependency to ToJson

deriving encodable + using json::PrettyEncoder removes the only ToJson trait implementation in the rust repository outside of libserialize
Remove outdated comment.

https://github.com/rust-lang/rust/pull/19472#issuecomment-65370278