- 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)

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

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

Fix bug in destructor for checker manager in DTC that caused segfaults on
exit.

Add a checker to dtc, based on a feature request from rwatson / brooks.
This checks that every node that has children specifies their register sizes.
This is not enabled by default, as the default sizes are sometimes required
(including by some DTS in the tree), but can help when writing new device
trees so that you can check that you actually meant the defaults.

Explicitly include headers that are implicitly included by libstdc++. Fixes
building dtc with libc++.

Import new (BSDL) device tree compiler. Now built by default, so that it can't
be used on the host system (and not installed on the device, if required). The
GPL'd one is still available if there are any devices that need it (make
universe passes with it, including kernels that use fdt, but there may be some
out-of-tree ones). WITH_GPL_DTC can be used to select the old one, for now.

Probably won't be MFC'd, but we'll remove the GPL'd version in head after the
new one has had a lot more testing and ship it in 10.0.