Thread ids now contain their container ids in the top 2 nibbles.
Threads on other containers can be addressed by changing those
two nibbles. The addressing of inter-container threads are
subject to capabilities.
Changes:
It is now possible to use do_mmap() from within mm0.
- pager_new_virtual()/delete_virtual() return addresses that are
disjoint from find_unmapped_area() used by mmap() interface for
anonymous or not-fixed areas.
- find_unmapped_area() now uses task->map_start task->map_end instead
of task->start and task->end. task->start/end are still valid task
space addresses for mmap(), but finding a new address is limited to
map_start/map_end.
- We have both interfaces because mmap() is only useful for backed-files.
When the pager needs to access a user memory range for example, that is
not backed by a file and thus we need to use pager_new_virtual() instead
of mmap() for mapping.
