Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Assume a big-endian default on MIPS and drop the "eb" suffix from MACHINE_ARCH.
This makes our naming scheme more closely match other systems and the
expectations of much third-party software. MIPS builds which are little-endian
should require and exhibit no changes. Big-endian TARGET_ARCHes must be
changed:
From: To:
mipseb mips
mipsn32eb mipsn32
mips64eb mips64

An entry has been added to UPDATING and some foot-shooting protection (complete
with warnings which should become errors in the near future) to the top-level
base system Makefile.

o) Use ABI, not ISA_* options, to determine whether to compile bits if libkern
required for the ABI the kernel is being built for.
XXX This is implemented in a kind-of nasty way that involves including source
files, but it's still an improvement.
o) Retire ISA_* options since they're unused and were always wrong.

Remove the 'machine mips' from DEFAULTS. Put the proper 'machine mips
mipsel' or 'machine mips mipseb' into the config file (with a few 64's
tossed in for good measure). This will let us build the proper
kernels with different worlds as part of make universe.