Add two more software events that are common to many cpus.

Alignment faults: When a load or store is not aligned properly.

Emulation faults: When an instruction is emulated in software.

Both cause a very significant slowdown (100x or worse), so identifying and
fixing them is very important.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>