fix attribute mem leaks in landslide.c
Add support to cause_timer_interrupt_immediately from userspace. Untested.
definegen: emit addresses for user binary (XXX: what if user prog binary is missing?)
Add userspace kern_specifics hooks for user malloc and ELF regions
Oooooops. Damn signed/unsigned errors.
Make stack trace half-work (no symtable yet) in userspace
Check for userspace panics
Don't require size param for kernel LMM free() since, user mm_free() doesn't have size.
fix MORE stupid signedness bugs in MEM_TRANSLATE
Track user_mem in addition to kern_mem. TODO: Have a switch to toggle userspace/kernel for independence purposes.
Add tell_landslide_execing tell.
Track user cr3s and did_exec; check user accesses by VA not PA.
Don't track did_exec; cr3s is sufficient if other stuff (VA not PA) is implemented correctly
Revert "Add tell_landslide_execing tell."

This reverts commit b2297c24169b1739ff48354ed0d7e0b8a735d314.
cosmetic changes for unknown symtable results
Forgive userspace mm_init its sins.
Split out user specifics and add hooks for user thrlib, mutexes, etc.
add separate lockset per thread for user vs kern. unused yet.
fix bugge
Add TESTING_USERSPACE flag, control which shm heap is filled, and call sched_update() and friends indiscriminately w.r.t USER_MEM_START.