auto merge of #10153 : nikomatsakis/rust/issue-4846-multiple-lifetime-parameters...

Fully support multiple lifetime parameters on types and elsewhere, removing special treatment for `'self`. I am submitting this a touch early in that I plan to push a new commit with more tests specifically targeting types with multiple lifetime parameters -- but the current code bootstraps and passes `make check`.

Fixes #4846

diff --cc src/librustc/lib.rs
Simple merge

diff --cc src/librustc/metadata/encoder.rs
Simple merge