Add support for gdb's memory searching capabilities to our in-kernel gdb
server.

Submitted by:	Daniel O'Connor <daniel.oconnor@isilon.com>
Reviewed by:	jhb
Sponsored by:	EMC Isilon Storage Division
Clarify a diagnostic printf() in the mbuf code: M_EXT doesn't necessarily
imply a cluster is attached; it could also refer to some other sort of
external storage (e.g., an sf_buf).

MFC after:	3 days
Sponsored by:	EMC / Isilon Storage Division
Garbage collect NFSMINOFF() from the NFS stack; this unused macro replicates
mbuf-initialisation logic that is best left to centralised mbuf utility
code rather than scattered around the kernel.

MFC after:	3 days
Sponsored by:	EMC / Isilon Storage Division
Correct patch paths (remove contrib/llvm/)

The example in contrib/llvm/patches/README.TXT fails otherwise.

Sponsored by:	DARPA, AFRL
Add the fp{get,set}{mask,round} functions to the public symbols in the map.
These are only exported for armv6hf as the soft-float ABIs have these in
the softfloat Symbol.map file.
vt_vga: vd_setpixel_t and vd_drawrect_t are noop in text mode

MFC after:	3 days
Add the virtual timer irq to the list of interrupts we enable on secondary
cores.
Set vnet context before accessing V_socket_hhh[].

Submitted by:	"Hiroo Ono (小野寛生)" <hiroo.ono+freebsd gmail.com>
Merge remote-tracking branch 'freebsd/master' into hardened/current/segvguard