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)

Correct typos (s/OFERFLOW/OVERFLOW/).

Reviewed by: jhb

Allow fast instruction and data access mmu miss traps to be handled by
user trap handlers.

Don peril sensitive sun glasses and change the default system call vector
for sparc64 from trap #9 to trap #65. This is one of the ABI "blessed"
system call vectors and is different from any other system that we might
want to emulate, making the emulation easier by reducing the number of
code paths that need to be shared. Compatibility with old applications
is provided with COMPAT_FREEBSD4.
Add defines for a few special traps that we may need to implement for
compatibility with 32bit applications, and add comments on which vectors
are used for what in other systems, and which are available.
Pass magic flags to trap() for deprecated or unimplemented system call
vectors so they will deliver SIGSYS instead of SIGILL.

This piggy backs nicely with the recent sigaction(2) system call number
change, and provided the rules are followed for upgrading past it, this
change should not be noticed.

Add a define for the fp restore soft trap type.
Only declare C things if __ASM__ is not defined.

Add a header for user trap types required by the sparc abi.
For simplicity the corresponding kernel types use the same
numerical values.