Initial page fault handling

Signed-off-by: mjanikok <janimikokkonen@gmail.com>
implement fixup fault and backtrace which is the first simple user.

Signed-off-by: mjanikok <janimikokkonen@gmail.com>
allow execution to flow until main_cont
so we can reach the backtrace.

Signed-off-by: mjanikok <janimikokkonen@gmail.com>