ack parser.parse_ty change in quote_ty! (+ test)
auto merge of #19463 : kali/rust/master, r=alexcrichton

parse_ty() no longer takes a boolean parameter. quote_ty! implementation has not yet been modified accordingly. 

As a matter of fact, quote_ty! was not covered by tests. One test (called qquotes) references it, but it has been ignored for nearly one year and now need heavy refactoring.

quote_token.rs seemed like a good place to test quote_ty!, many other quote_*! macros were asserted there.
Add parser support for generalized where clauses

Implement support in the parser for generalized where clauses,
as well as the conversion of ast::WherePredicates to
ty::Predicate in `collect.rs`.