Add support for freeing node data when freeing a queue
Add support for freeing contexts
Add simple application for testing the syscalls as they are implemented
Remove debug syscall from the idle thread loop
Add support for freeing threads
Add support for freeing processes
Add support for removing threads from processes
Add support for removing threads from the scheduler

Also add support for allocating and freeing PIDS and various small
scheduler changes.
Add syscalls 0 (system) and 1 (thread exit)