. VM needs a higher priority than VFS, PM etc

 . VM needs a higher priority than VFS, PM etc
 . introduce FULLVM flag: MEMORY and the initial MFS
   get their own full address spaces, making their stacks
   and heaps not preallocated (well, freed after VM has
   initialized it) and letting them allocate more dynamically.
   MEMORY in particular needs this to map in physical memory
   using its own page table, without having to allocate.