Pull up following revision(s) (requested by rin in ticket #1456):

sys/kern/sys_ptrace_common.c: revision 1.73

Fix regression introduced to ptrace_regs() in rev 1.27:
http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/kern/sys_ptrace_common.c#rev1.27

Size of registers should be determined from tracer, NOT tracee.

Now, 64-bit tracer can manipulate registers of 32-bit tracee again.
gdb for amd64 works for i386 binaries to some extent.

XXX
pullup to netbsd-9 and -8.

(martin)