pci: add a new pci_child_added newbus method.

This is needed so when running under Xen the calls to pci_child_added
can be intercepted and a custom Xen method can be used to register
those devices with Xen. This should not include any functional
change, since the Xen implementation will be added in a following
patch and the native implementation is a noop.

Sponsored by: Citrix Systems R&D
Reviewed by: jhb

dev/pci/pci.c:
dev/pci/pci_if.m:
dev/pci/pci_private.h:
dev/pci/pcivar.h:
 - Add the pci_child_added newbus method.
netback: fixes for netback

This patch contains the following fixes for netback:
 - Only unbind the evtchn if it has been bound.
 - Set xnb->bridge to NULL after free to prevent double-freeing it.
 - Set the MAC address for the host-facing interface to a dummy value.

Sponsored by: Citrix Systems R&D

dev/xen/netback/netback.c:
 - Prevent trying to unbind if the evtchn has not been bounded.
 - Prevent double-freeing xnb->bridge.
 - Set the MAC address of the host-facing interface to a dummy value,
   so it can work when the interface is added to a bridge.
vt(4): Give the window to vd_bitblt_text_t callback

... instead of both the buffer and the font. Again, this simplifies the
API.

MFC after:	1 week
netback: remove dead code

Remove the xen_net_read_mac function since it's not used anymore.

Sponsored by: Citrix Systems R&D
vt(4): The offset to center the text area is per-window now

The previous global offset, based on the last loaded font, had no
meaning for other windows. This caused a shifted text area, often partly
out-of-screen.

MFC after:	1 week
xen: fix incorrectly accounted free

Fix some frees incorrectly assigned to M_XENBUS when the memory is
allocated with M_XENSTORE.

Sponsored by: Citrix Systems R&D
MFC after:	1 week

dev/xen/blkback/blkback.c:
 - Fix incorrect frees.
vt(4): Don't run vt_set_border() and vt_flush() concurrently

In the case of vt_vga, the two concurrent calls were writing to the same
VGA registers, causing incorrect refresh of the screen.

MFC after:	1 week
vt_vga: Remove a "FIXME" comment; the issue was solved in r270338

MFC after:	1 week
vt(4): Use the actual size of the mouse when marking its position as dirty

This fixes a bug where part of the cursor was not erased.

MFC after:	1 week
vt(4): Remove "FIXME" about multiple locking of vt_buf in vt_flush()

After some testing, it appears that acquiring the lock once and keeping
it longer is slower than taking it multiple times.

While here, fix a typo in another comment.

MFC after:	1 week
In do_lock_pi(), do not override error from umtxq_sleep_pi() when
doing suspend check.  This restores the pre-r251684 behaviour, to
retry once after the signal is detected.

PR:	kern/192918
Submitted by:	Elliott Rabe, Dell Inc., Eric van Gyzen <eric@vangyzen.net>
Obtained from:	Dell Inc.
MFC after:	1 week
Update to the Intel Base driver for the Intel XL710 Ethernet Controller Family
	- It was decided to change the driver name to if_ixl for FreeBSD
	- This release adds the VF Driver to the tree, it can be built into
	  the kernel or as the if_ixlv module
	- The VF driver is independent for the first time, this will be
	  desireable when full SRIOV capability is added to the OS.
	- Thanks to my new coworker Eric Joyner for his superb work in
	  both the core and vf driver code.

Enjoy everyone!

Submitted by:	jack.vogel@intel.com and eric.joyner@intel.com
MFC after:	3 days (hoping to make 10.1)
Restore historical behavior of in_control, which, when no matching address
is found, the first usable address is returned for legacy ioctls like
SIOCGIFBRDADDR, SIOCGIFDSTADDR, SIOCGIFNETMASK and SIOCGIFADDR.

While there also fix a subtle issue that a caller from a jail asking for
INADDR_ANY may get the first IP of the host that do not belong to the jail.

Submitted by:	glebius
Differential Revision: https://reviews.freebsd.org/D667
Add some missing checks for unsupported interfaces (e.g. pflog(4)) when
handling ioctls. While here, remove duplicated checks for a NULL ifp in
in6_control(): this check is already done near the beginning of the
function.

PR:		189117
Reviewed by:	hrs
MFC after:	2 weeks
Suppress warnings when retrieving protocol stats from interfaces that
don't support IPv6 (e.g. pflog(4)).

Reviewed by:	hrs
MFC after:	2 weeks
Make DTrace stuff compile with C99 standard.