This commit cleans out a large amount of deprecated APIs from the standard
library and some of the facade crates as well, updating all users in the
compiler and in tests as it goes along.
Some compile-fail tests illustrated cases to be rejected by dropck,
including ones that check cyclic data cases designed to exposed bugs
if they are actually tricked into running by an unsound analysis.
E.g. these exposed bugs in earlier broken ways of handling `Vec<T>`.
(Note that all the uses of `unsafe_destructor` are just placating the
simple analysis used for that feature, which will eventually go away
once we have put the dropck through its paces.)
