[$] Willy's memory-management to-do list

Matthew "Willy" Wilcox has been doing a fair amount of work in thememory-management area recently. He showed up at the 2018 Linux Storage,Filesystem, and Memory-Management Summit with a list of discussion topicsrelated to that work; it was enough to fill a plenary session with somespillover into the memory-management track the next day. Some of histopics were fairly straightforward; others look to be somewhat moreinvolved.