- 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 r261799: Add bounds check for pteindex / pdeindex to amd64 kvm_minidump

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

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

libkvm code janitoring

- make WARNS=6 clean for archs w/o strict alignment requirments
- add const, ANSIfy, remove unused vars, cast types for comparison
- thanks to differing definitions of VM_MIN_ADDRESS across our archs, we
need to trick the compiler to not complain about signedness. We could
either fix VM_MIN_ADDRESS to always be a simple integer or make the
check conditional on $ARCH.

Closes PRs: kern/42386, kern/83364
Reviewed by: bde

amd64: introduce minidump version 2

After KVA space was increased to 512GB on amd64 it became impractical
to use PTEs as entries in the minidump map of dumped pages, because size
of that map alone would already be 1GB.
Instead, we now use PDEs as page map entries and employ two stage lookup
in libkvm: virtual address -> PDE -> PTE -> physical address. PTEs are
now dumped as regular pages. Fixed page map size now is 2MB.

libkvm keeps support for accessing amd64 minidumps of version 1.
Support for 1GB pages is added.

Many thanks to Alan Cox for his guidance, numerous reviews, suggestions,
enhancments and corrections.

Reviewed by: alc [kernel part]
MFC after: 15 days

Fix missing includes of <string.h>, to silence some compiler warnings.

Submitted by: Pawel Worach

_kvm_malloc allocates memory through calloc() which
returns zeroed memory, so don't redo the initialization.

Include strings.h for bzero()

Teach libkvm how to read minidumps. It turns out that minidumps are
far more convenient for libkvm to work with because of the page table
block at the beginning. As a result, the MD code is smaller.

libkvm will automatically detect old vs mini dumps on i386 and amd64.

libkvm will handle i386 PAE and non-PAE modes. There is a PAE flag in
the i386 minidump header to signal the width of the entries in the
page table block.

Other convenient values are also present, such as kernbase and the direct
map addresses on amd64.