Increase kernel stack size to 2mb, move from cooperative to timer

preemption based scheduling, add correct save_lock on aarch64, add
simple IPC (read, write, manage), and simple and unsecure SHM, add
per-process kernel stacks, add copy_cstr_to_user, always use run_next
for aarch64, remove primitives from the kernel

config.mk

@@ -1,4 +1,4 @@
-export KARCH ?= x86_64
+export KARCH ?= aarch64
 export OUTPUT ?= kernel
-export MEMORY ?= 4G
+export MEMORY ?= 1G
 export TIMER_FREQUENCY_HZ ?= 1000