Minor doc fixes in various places
Fix typo in libcore
Rename Result.unwrap_or_handle() to .unwrap_or_else()

Result.unwrap_or_handle() is the equivalent of Option.unwrap_or_else().
In the interests of naming consistency, call it the same thing.

[breaking-change]
Silence warning in RefCell test suite
Add AST node for pattern macros
Add patterns to MacResult
Expand macros in patterns
Parse macros in patterns

Fixes #6830.
Add a test for macros in patterns