This removes most explicit uses of the + argument mode. Pending a
snapshot, I had to remove the forbid(deprecated_modes) pragma from
a bunch of files. I'll put it back!
+ mode still has to be used in a few places for functions that get
moved (see task.rs)
The changes outside core and std are due to the to_bytes trait and
making the compiler (with legacy modes on) agree with the libraries
(with legacy modes off) about modes.
Everything should now call ptr::addr_of instead of
ptr::p2::addr_of. Only the pipes macro code when compiled
by stage0 will call ptr::p2::addr_of. Needs a snapshot to get
rid of that.
Currently, the new version is ptr::p2::addr_of and the old one is
ptr::addr_of. This is kind of cheesy, but I need a snapshot before I
can ditch the old version, since the pipe compiler generates calls to
addr_of.
core is converted over to use the new version, std is not.
