Use ICMP6STAT_INC() macro for ICMPv6 errors accounting.

MFC after:	2 weeks
Alphabetize includes.
Alphabetize reserved-word (resword) registration.
Whitespace and comments.
Whitespace.
Style -- no ;; needed on fallback clause within case-statement.
Fix a couple of typos that broke buildworld for me.

Reviewed by:	peter
Use RIP6STAT_INC() macro for raw ip6 statistics accounting.

MFC after:	2 weeks
Use PIM6STAT_INC() and MRT6STAT_INC() macros for IPv6 multicast
statistics accounting.

MFC after:	2 weeks
Mark geom_mirror as capable of unmapped i/o

Obtained from:	Netflix
MFC after:	3 days
Fix a mystery cut-n-paste corruption from the previous commit.

Submitted by:	Brenden Fabeny
Rename some prefixes in the Block Group Descriptor fields to ext4bgd_

Change prefix to avoid confusion and denote that these fields
are generally only available starting with ext4.

MFC after:	3 days
Try to fix build of apr on FreeBSD/arm.
Only enable svn on amd64/ia64/sparc64/i386.
- Add CIDR notation support like 192.168.1-2.10-16/24 to $ifconfig_IF_aliasN.
  This is an extended version of ipv4_addr_IF which supports both IPv4 and
  IPv6, and multiple range specifications.  To avoid to generate too many
  addresses, the maximum number of the generated addresses is currently
  limited to 31.

- Add $ifconfig_IF_aliases, which accepts multiple IP aliases in a variable.

- ipv6_prefix_IF now supports !/64 prefix length.  In addition to the old
  64-bit format (2001:db8:1:1), a full 128-bit format like 2001:db8:1:1::/64
  is supported.

- Replace ifconfig command with $IFCONFIG_CMD variable to support
  a dry-run mode in the future.

- Remove IP aliases before removing all of IPv4 addresses when doing
  "rc.d/netif down".

- Add a DAD wait to network6_getladdr() because it is possible to fail to
  configure an EUI64 address when ipv6_prefix_IF is specified.

A summary of the supported ifconfig_* variables is as follows:

 # IPv4 configuration.
 ifconfig_em0="inet 192.168.0.1"
 # IPv6 configuration.
 ifconfig_em0_ipv6="inet6 2001:db8::1/64"
 # IPv4 address range spec.  Now deprecated.
 ipv4_addr_em0="10.2.1.1-10"
 # IPv6 alias.
 ifconfig_em0_alias0="inet6 2001:db8:5::1 prefixlen 70"
 # IPv4 alias.
 ifconfig_em0_alias1="inet 10.2.2.1/24"
 # IPv4 alias with range spec w/o AF keyword (backward compat).
 ifconfig_em0_alias2="10.3.1.1-10/32"
 # IPv6 alias with range spec.
 ifconfig_em0_alias3="inet6 2001:db8:20-2f::1/64"
 # ifconfig_IF_aliases is just like ifconfig_IF_aliasN.
 ifconfig_em0_aliases="inet 10.3.3.201-204/24 inet6 2001:db8:210-213::1/64 inet 10.1.1.1/24"
 # IPv6 alias (backward compat)
 ipv6_ifconfig_em0_alias0="inet6 2001:db8:f::1/64"
 # IPv6 alias w/o AF keyword (backward compat)
 ipv6_ifconfig_em0_alias1="2001:db8:f:1::1/64"
 # IPv6 prefix.
 ipv6_prefix_em0="2001:db8::/64"

Tested by:	Kimmo Paasiala
Add debugging (for a case that shouldn't arise, but makes it more obvious
if a menu addition is made in one plce but forgotten in another).
Remove pedanticism and consolidate some logic.
When the fall-back of a case-statement is the last thing executed in a
while-loop _and_ all prior matches in the same case-statement either break
or continue, we can safely break the fall-back out of the case-statement.
This should improve readability and allow for longer-lines by reducing the
level of indentation by-one for the fall-back case.
When the fall-back of a case-statement is the last thing executed in a
while-loop _and_ all prior matches in the same case-statement either break
or continue, we can safely break the fall-back out of the case-statement.
This should improve readability and allow for longer-lines by reducing the
level of indentation by-one for the fall-back case.
(a continuation of SVN r252019)
Fix a code typo in a case-statement match expression that prevented IPv6
URLs with port designator from working properly (e.g. http://[::1]:80/).