Make 'self lifetime illegal.

Also remove all instances of 'self within the codebase.

This fixes #10889.

To make reviewing easier the following files were modified with more than a dumb text replacement:

- `src/test/compile-fail/lifetime-no-keyword.rs`
- `src/test/compile-fail/lifetime-obsoleted-self.rs`
- `src/test/compile-fail/regions-free-region-ordering-incorrect.rs`
- `src/libsyntax/parse/lexer.rs`