[$] Hastening process cleanup with process_mrelease()

One of the fundamental invariants of computing is that, regardless of howmuch memory is installed in a system, it is never enough. This isespecially true of systems with tight performance constraints, where everypage of memory is allocated and in use, making it difficult to findmore when it is badly needed. One way to make more memoryavailable is to kill one or more processes, freeing their resources forother users. But that often does not work as quickly or reliably as userswould like. In an attempt to improve the situation, Suren Baghdasaryan hasproposedthe addition of a system call named process_mrelease().