Fix an ICE when dereferencing types which cannot be dereferenced
syntax: de-mode and prepare for de-modeing rustc
rustc: de-mode + fallout from libsyntax changes
Assorted fixes from de-modeing rustc/syntax (rusti, rustdoc, fuzzer, rustpkg)
core: clean up tests (mostly unused unsafe blocks)
std: clean up tests (mostly unused unsafe blocks)