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

- Merge macros depending on the flags being preserved between calls
into a single "__asm"-statement as GCC doesn't guarantee their
consecutive output even when using consecutive "__asm __volatile"-
statement for them. Remove the otherwise unnecessary "__volatile". [1]
- The inline assembler instructions used here alter the condition
codes so add them to the clobber list accordingly.
- The inline assembler instructions used here uses output operands
before all input operands are consumed so add appropriate modifiers.

Pointed out by: bde [1]
MFC after: 2 weeks

- Fix spelling and style.
- Use __FBSDID.

Remove advertising clause from University of California Regent's
license, per letter dated July 22, 1999 and email from Peter Wemm,
Alan Cox and Robert Watson.

Approved by: core, peter, alc, rwatson

Add optimized implementations of in_cksum_skip() and related functions
for sparc64.