MFC r248825, 248775

Add unmapped i/o support for the mps and isci drivers.

Submitted by:	mav, jimharris
Obtained from:	Netflix
Fix a bug that allowed a tracing process (e.g. gdb) to write
to a memory-mapped file in the traced process's address space
even if neither the traced process nor the tracing process had
write access to that file.

Security:	CVE-2013-2171
Security:	FreeBSD-SA-13:06.mmap
Approved by:	so
MFC r248068 (by sbruno):
Add legacy support to geom raid to create a /dev/arX device for support
of upgrading older machines using ataraid(4) to newer releases.

This optional parameter is controlled via kern.geom.raid.legacy_aliases
and will create a /dev/ar0 device that will point at /dev/raid/r0 for
example.

Tested on Dell SC 1425 DDF-1 format software raid controllers installing from
stable/7 and upgrading to stable/9 without having to adjust /etc/fstab
MFC r248295 (by pjd):
We don't need buffer to handle BIO_DELETE, so don't check buffer size for it.
This fixes handling BIO_DELETE larger than MAXPHYS.
MFC r248596 (by kib):
Correct the page count when excess length is trimmed from the bio.
MFC r248696:
Make GEOM MULTIPATH to report unmapped bio support if underling path report
it.  GEOM MULTIPATH itself never touches the data and so transparent.
MFC r248720:
Remove extra bio_data and bio_length copying to child request after calling
g_clone_bio(), that already copied them.
MFC r248721:
GEOM NOP does not touch the data, so pass G_PF_ACCEPT_UNMAPPED flag through.
MFC r248722:
geom_slice.c and its consumers like GEOM_LABEL are not touching the data
unless hotspots are used.  Pass G_PF_ACCEPT_UNMAPPED flag through except
such rare cases (obsolete GEOM_SUNLABEL and GEOM_BSD).
MFC r249193 (by trasz):
Make it possible to submit FLUSH bios through geom_dev strategy.  This
is required for CTL to work with device-backed LUNs.
MFC r249974:
Return "descr" field alike to "Intel RAID1 volume" for GEOM RAID to make
it look better in bsdinstall.
MFC r251616:
Don't update provider properties and don't set DISKFLAG_OPEN if d_open()
disk method call returned error.  GEOM considers devices in such case as
still closed, and won't call symmetric d_close() for them.