- Copy stable/10@296371 to releng/10.3 in preparation for 10.3-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.3.
- Update default pkg(8) configuration to use the quarterly branch.

Approved by: re (implicit)

MFC revisions 268999, 269027, 269351-269352, 269354, 269460, 270283,
270505, 270954, and 270989:
r268999: Add new bsdconfig example scripts; remove obsolete ones
r269027: Update bsdconfig dot module; fixes and enhancements
r269351: Add setvar() for non-FreeBSD platforms using bash as /bin/sh
r269352: Fix syntax error when run under bash
r269354: Update setvar() function introduced in r269351
r269460: Update f_xdialog_info() in bsdconfig's dialog.subr include
r270283: Add `-A' flag to pkg-install(8) when installing dependencies
r270505: Optimize f_which() to be slightly faster still (common.subr)
r270954: Update f_dialog_init() for safer getopts usage (dialog.subr)
r270989: Fix for previously mentioned r270954

Approved by: re (gjb)

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Re-implement $probe_only aspect of f_media_get_TYPE() (where TYPE is cdrom,
nfs, ftp, http, httpproxy, etc.) and f_device_get() (abstract method for
calling aforementioned f_media_get_TYPE()).

Previously, if $probe_only was present and non-NULL, the TYPE functions
would check for $file and exit with an appropriate error status (success if
the file exists and readable, failure otherwise).

While this has been retained, a pair of globals has been introduced:
$PROBE_EXIST and $PROBE_SIZE (see `/usr/share/bsdconfig/media/common.subr')

The $PROBE_EXIST global can be used where you need the functionality of
simply testing for existence (previously the _only_ functionality).

Meanwhile, the new $PROBE_SIZE global can be used to cause the TYPE function
to print the size of the file (in bytes) on standard-out (or -1) if not
found or an error occurs. NOTE: If an error occurs, it is logged with the
dprintf function, which is visible with `-d' flag or debug=1.

In many cases, where you need to get the size of a file _and_ check for its
existence, you can use the return status of a $PROBE_SIZE call.

Fix typos in the BSD License.

Be consistent with other usr.sbin programs w/respect to the copyright
wording ("All rights reserved."); I had the casing wrong on many instances.

Implement the $probe_only parameter (previously unimplemented).

Fine-tune the parsing of the URL. Re-order, comment, and add debugging to
each case of unique URL format.

Take advantage of the fact that f_getvar evaluates the $var_to_get parameter
within braces, allowing all manner of parameter expansions (properly quoted
or escaped, of course).

Alphabetize library includes.

Style.

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/).

Import media selection/preparation framework (sysinstall inspired). Makes
accessing files from various types of media nice and abstracted away from
the wet-work involved in preparing, validating, and initializing those
types of media. This will be used for the package management system module
and other modules that need access to files and want to allow the user to
decide where those files come from (either in a scripted fashion, prompted
fashion, or any combination thereof).

Heavily inspired by sysinstall and even uses the same reserved words so
that scripts are portable. Coded over months, tested continuously through-
out, and reviewed several times.

Some notes about the changes:
- Move network-setting acquisition/validation routines to media/tcpip.subr
- The options screen from sysinstall has been converted to a dialog menu
- The "UFS" media choice is renamed to "Directory" to reflect how sysinstall
treats the choice and a new [true] "UFS" media choice has been added that
acts on real UFS partitions (such as external disks with disklabels).
- Many more help files have been resurrected from sysinstall (I noticed that
some of the content seems a bit dated; I gave them a once-over but they
could really use an update).
- A total of 10 media choices are presented (via mediaGetType) including:
CD/DVD, FTP, FTP Passive, HTTP Proxy, Directory, NFS, DOS, UFS, Floppy, USB
- Novel struct/device management layer for managing the issue of passing
more information than can comfortably fit in an argument list.