Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

- Include <machine/utrap.h> so this header doesn't have an MD
dependency.
- Make prototypes style(9) compliant.

MFC after: 1 week

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

Provide sysarch(2) prototypes in the MD sysarch.h headers. While I'm
at it, use the ANSI C generic pointer type for the second argument,
thus matching the documentation.

Remove the now extraneous (and now conflicting) function declarations
in various libc sources. Remove now unnecessary casts.

Reviewed by: bde

Add support for an alternate signal trampoline; add a sysarch call to register
an alternate trampoling with the kernel.

Implement sysarch(SPARC_UTRAP_INSTALL).

Forgot this file in last commit.