The parser now warns about use of mutbl-ref mode, though it's kind
of a lie since this commit doesn't remove support for the mode.
Changed move_val_init to have stage0 and stage1/2 versions, the latter of
which is demoded.
Changed the type that the typechecker expects the move_val_init
intrinsic to have. After this is pushed, I can make a new snapshot,
which will remove the need for the stage0 versions.
What we now do is to create a region variable for each &
expression (and also each borrow). The lifetime of this
variable will be checked by borrowck to ensure it is not greater
than the lifetime of the underlying data. This both leads to
shorter lifetimes in some cases but also longer in others,
such as taking the address to the interior of unique boxes
tht are rooted in region pointers (e.g., returning a pointer
to the interior of a sendable map).
This may lead to issue #2977 if the rvalue is not POD, because
we may drop the data in trans sooner than borrowck expects us
to. Need to work out precisely where that fix ought to occur.
