Solution 4: Create rvalue reference types as REFERENCE_TYPE nodes and
include them in the TYPE_NEXT_REF_TO lists but in such a way that that
they are hidden from current TYPE_NEXT_REF_TO logic and won't interfere
with existing code.
Solutions 1 and 4 are the easiest to implement. Solutions 3 and 4 seem
kludgy to me in the way that they fiddle with middle end data structures
from the front end, but I think I'm the only one who feels that way. I'm
willing to do whatever, I'd just like somebody to tell me which
direction to go. Solution 4 seems like the path of least resistance at
this point, are there any objections to that?