Pull up following revision(s) (requested by riastradh in ticket #283):

usr.sbin/crash/arch/powerpc.c: revision 1.1
sys/arch/powerpc/powerpc/db_trace.c: revision 1.61
sys/arch/powerpc/powerpc/db_trace.c: revision 1.62
sys/arch/powerpc/powerpc/db_trace.c: revision 1.63
usr.sbin/crash/crash.c: revision 1.15
sys/arch/powerpc/powerpc/db_disasm.c: revision 1.30
sys/arch/powerpc/powerpc/db_disasm.c: revision 1.31
usr.sbin/crash/arch/generic.c: revision 1.2
usr.sbin/crash/Makefile: revision 1.47
usr.sbin/crash/arch/powerpc64.c: revision 1.1

crash(8): Add powerpc support.

powerpc/ddb: Use db_read_bytes, not direct pointer access.
Mark some powerpc-variant ifdefs with XXX crash(8), not sure yet what
to do about them.

powerpc/ddb: Fix one more load to use db_read_bytes.
Fix some typos in crash(8) comments too.

(martin)