(split) Add support for virtual cores (aka minidumps). To that end, refactor this
file as follows:
1.  Common ia64-specific support functions have the ia64_ prefix.
2.  Functions that work on physical cores have the phys_ prefix.
3.  Functions that work on virtual cores have the virt_ prefix.

With that:
1.  _kvm_kvatop() has been renamed to phys_kvatop() as it handles
    physical cores only.
2.  The new _kvm_kvatop() is nothing but a wrapper that calls either
    phys_kvatop() or virt_kvatop() by virtue of the kvatop function
    pointer in the vmstate structure.
3.  virt_kvatop() is nothing but a wrapper around virt_addr2off().
4.  virt_addr2off() iterates over the Phdrs to find the segment in
    which the address falls and return the file offset for it.

Now it's up to the kernel to populate the core file appropriately.
(split) In sys/dev/usb/wlan/if_urtw.c, #if 0 a static const variable, which has
been unused since r198194.

MFC after:	3 days
(split) Add support for the MediaTek/Ralink RT3593 chipset.
Committed over the ZyXEL NWD2705 on amd64 with WPA.
(split) Merge branch 'CURRENT' (commit '83ac6854')

Conflicts:
	sys/dev/usb/wlan/if_run.c