- Copy stable/10@285827 to releng/10.2 in preparation for 10.2-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.2.
- Update default pkg(8) configuration to use the quarterly branch.[1]

Discussed with: re, portmgr [1]
Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

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

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

Add ia64_sync_icache() and use it to make the I-cache coherent
after loading the kernel's text segment. The kernel will do the
same for loaded modules, so don't worry about that.

Use the new arch_loadaddr I/F to align ELF objects to PBVM page
boundaries. For good measure, align all other objects to cache
lines boundaries.

Use the new arch_loadseg I/F to keep track of kernel text and
data so that we can wire as much of it as is possible. It is
the responsibility of the kernel to link critical (read IVT
related) code and data at the front of the respective segment
so that it's covered by TRs before the kernel has a chance to
add more translations.

Use a better way of determining whether we're loading a legacy
kernel or not. We can't check for the presence of the PBVM page
table, because we may have unloaded that kernel and loaded an
older (legacy) kernel after that. Simply use the latest load
address for it.

MFaltix:
Add support for Pre-Boot Virtual Memory (PBVM) to the loader.

PBVM allows us to link the kernel at a fixed virtual address without
having to make any assumptions about the physical memory layout. On
the SGI Altix 350 for example, there's no usuable physical memory
below 192GB. Also, the PBVM allows us to control better where we're
going to physically load the kernel and its modules so that we can
make sure we load the kernel in memory that's close to the BSP.

The PBVM is managed by a simple page table. The minimum size of the
page table is 4KB (EFI page size) and the maximum is currently set
to 1MB. A page in the PBVM is 64KB, as that's the maximum alignment
one can specify in a linker script. The bottom line is that PBVM is
between 64KB and 8GB in size.

The loader maps the PBVM page table at a fixed virtual address and
using a single translations. The PBVM itself is also mapped using a
single translation for a maximum of 32MB.

While here, increase the heap in the EFI loader from 512KB to 2MB
and set the stage for supporting relocatable modules.

Remove LDR_LOG2_PGSZ, ia64_pgtbl and ia64_pgtblsz. They are part of
a WIP and not used yet.

Major rework of the ia64 loaders. The two primary objectives are:
1. Make libefi portable by removing ia64 specific code and build
it on i386 and amd64 by default to prevent regressions. These
changes include fixes and improvements over previous code to
establish or improve APIs where none existed or when the amount
of kluging was unacceptably high.
2. Increase the amount of sharing between the efi and ski loaders
to improve maintainability of the loaders and simplify making
changes to the loader-kernel handshaking in the future.

The version of the efi and ski loaders are now both changed to 1.2
as user visible improvements and changes have been made.