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

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

Follow up to r225203 refining break-to-debugger run-time configuration
improvements:

(1) Implement new model in previously missed at91 UART driver
(2) Move BREAK_TO_DEBUGGER and ALT_BREAK_TO_DEBUGGER from opt_comconsole.h
to opt_kdb.h (spotted by np)
(3) Garbage collect now-unused opt_comconsole.h

MFC after: 3 weeks
Approved by: re (bz)

Rewrite of puc(4). Significant changes are:
o Properly use rman(9) to manage resources. This eliminates the
need to puc-specific hacks to rman. It also allows devinfo(8)
to be used to find out the specific assignment of resources to
serial/parallel ports.
o Compress the PCI device "database" by optimizing for the common
case and to use a procedural interface to handle the exceptions.
The procedural interface also generalizes the need to setup the
hardware (program chipsets, program clock frequencies).
o Eliminate the need for PUC_FASTINTR. Serdev devices are fast by
default and non-serdev devices are handled by the bus.
o Use the serdev I/F to collect interrupt status and to handle
interrupts across ports in priority order.
o Sync the PCI device configuration to include devices found in
NetBSD and not yet merged to FreeBSD.
o Add support for Quatech 2, 4 and 8 port UARTs.
o Add support for a couple dozen Timedia serial cards as found
in Linux.

Let modules use the kernel's opt_*.h files if built along with
the kernel by wrapping all targets for fake opt_*.h files in
.if defined(KERNBUILDDIR). Thus, such fake files won't be
created at all if modules are built with the kernel.

Some modules undergo cleanup like removing unused or unneeded
options or .h files, without which they wouldn't build this way
or the other.

Reviewed by: ru
Tested by: no binary changes in modules built alone
Tested on: i386 sparc64 amd64

Change a directory layout for pc98.
- Move MD files into <arch>/<arch>.
- Move bus dependent files into <arch>/<bus>.
Rename some files to more suitable names.

Repo-copied by: peter
Discussed with: imp

o Remove opt_ddb.h from SRCS.
o Add opt_gdb.h and opt_kdb.h to SRCS.

Move to generating pccarddevs.h on the fly, both for the kernel and
the modules.

Also generate usbdevs.h automatically now, but a non-kernel file is
stopping that at the moment.

Remove the source file for the sio(4) EBus attachment here, too.

Fixed some style bugs:
- SRCS was totally disordered.
- the echos to create options headers were hidden using '@'.
- the args of echos to create options headers were single-quoted.
- the target names for the rules to create options headers were repeated.
- the unused option COMPAT_FREEBSD4 was put in opt_compat.h.

Fixed some style bugs. SRCS and the opt_*.h rules were totally
disordered. This commit only fixes the external disorder by
rearranging whole lines.

Fix to support pc98 and currect typo.

New sio module. A number of people have suggested this over the years
(most recently bde), so I'll commit the module I've had knocking
around in my tree for a while. This may have some rough edges, so if
you are able to build it on non-i386 platform (including pc98) please
let me know you succeeded. When I get enough reports, I'll connect it
to the build. If there are problems, feel free to fix them.

Suggested by: bde