Remove a bunch of methods that are superseded by if_inc_counter().

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.
Fix the handling of EOP in status descriptors for if_igb(4) and don't
double-free mbufs.

Like ixgbe(4) chipsets, EOP is only set on the final descriptor
in a chain of descriptors.  So, to free the whole list of descriptors,
we should free the current slot _and_ the assembled list of descriptors
that make up the fragment list.

The existing code was setting discard once it saw EOP + an error status;
it then freed all the subsequent descriptors until the next EOP. That's
totally the wrong order.
Reorder sysctls for spa.c global tunables; add sysctl for ccw_retry_interval.

MFC after:	1 month
Sponsored by:	Spectra Logic
- Use if_get_counter() to fetch ifnet statistics.
- Report IFCOUNTER_OQDROPS to linprocfs. Wasn't there before.

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.
simple_httpd: cosmetic cleanups.

Many tab vs space cleanups.
Use setpgid() instead of setpgrp() which is more portable,

MFC after:	5 weeks
Enable ZFS debug flags to be modified via vfs.zfs.debug_flags.

This is primarily only of interest to ZFS developers, but it makes it
easier to get additional debugging.

Submitted by:	gibbs
MFC after:	1 month
Sponsored by:	Spectra Logic
MFSpectraBSD:	517074 on 2011/12/15 (by will), 662343 on 2013/03/20 (by gibbs)
lpr: replace setpgrp(2) with setpgid(2).

setpgid(2) is more portable than setpgrp(2).
The BSD variant of setpgrp is a wrapper for
setpgid(2) anyways.

MFC after:	5 weeks
unistd: move setpgrp(2) to the __BSD_VISIBLE section

Our setpgrp(2) differs from the specified by POSIX, which
only has one argument, and is only meant for compatibility
with BSD.

Reference:
http://pubs.opengroup.org/onlinepubs/009695399/functions/setpgrp.html

Pointed-out in:	openbsd-tech (2014-09-16)
MFC after:	6 weeks
Silence noisy firewire logging.

MFC after:	1 month
Sponsored by:	Spectra Logic
MFSpectraBSD:	974594 on 2013/08/02
When updating device media size use cached cdevsw pointer.

Using pointer from the cdev directly is dangerous since we have no reference
on it, and it may change any time.  That caused panic if device has gone.

While there, report capacity change only if it really changed.

MFC after:	3 days
Start the process of cleaning up FreeBSD's firewire driver.

sys/dev/firewire/firewire.c:
sys/dev/firewire/firewire.h:
sys/dev/firewire/firewirereg.h:
sys/dev/firewire/fwcrom.c:
sys/dev/firewire/fwdev.c:
sys/dev/firewire/fwdma.c:
sys/dev/firewire/fwmem.c:
sys/dev/firewire/fwohci.c:
sys/dev/firewire/fwohci_pci.c:
sys/dev/firewire/fwohcivar.h:
sys/dev/firewire/if_fwe.c:
sys/dev/firewire/if_fwip.c:
sys/dev/firewire/sbp.c:
sys/dev/firewire/sbp_targ.c:
	Unifdef the code, removing support for DragonflyBSD
	and FreeBSD prior to version 5.

Submitted by:	gibbs
MFC after:	1 month
Sponsored by:	Spectra Logic
MFSpectraBSD:	1081188 on 2014/08/01
Use 'cc' for the C compiler instead of 'gcc'.

MFC after:	1 week
Sponsored by:	Spectra Logic
MFSpectraBSD:	1079507 on 2014/07/24
Make kernel to update LUN size from the backing storage on configuration
reload also if that size was not specified in the new configuration.

Previously it happened only if size was explicitly changed in config.

MFC after:	3 days
Remove debug.zfs_flags in favor of the new vfs.zfs.debug_flags.
Replace TUNABLE_INT with CTLFLAG_RWTUN.

Submitted by:	avg (debug.zfs_flags removal), smh (TUNABLE_INT replacement)
- Provide if_get_counter() method for vtnet(4).
- Do not accumulate statistics on every tick.
- Accumulate statistics in vtnet_setup_stat_sysctl()
  and in vtnet_get_counter().

Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.
Mechanically convert to if_inc_counter().
Add dtrace probe support for zfs SET_ERROR(..)

MFC after:	1 week
Sponsored by:	Multiplay
Mechanically convert to if_inc_counter().
Mechanically convert to if_inc_counter().
Mechanically convert to if_inc_counter().