sys: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

sys: Remove $FreeBSD$: one-line .h pattern

Remove /^\s*\*+\s*\$FreeBSD\$.*$\n/

sys/disk/*.h: Include sys/types.h

All these files use types defined by sys/types.h. Add an include of it
at the top to make them standalone.

Sponsored by: Netflix

Renumber copyright clause 4

Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.

Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96

Re-apply change 306811 or alternatively, revert change 307385.

Revert change 306811 so that the change can be re-done using
svn copy instead of svn move. This to preserve history on
the originals headers as well.

In order to allow mkimg(1) (and other tools) to become a build tool
that can be compiled on various OSes (including on older versions
of FreeBSD), make it possible to have it include the partitioning
scheme definitions without pulling in FreeBSD specifics.
In particular this means:
o move the scheme definitions iand related defines to header files
under sys/disk,
o make them (more) portable by using uint#_t (where applicable)
and renaming defines so that they at least have a good prefix,
o make the new headers stand-alone so that they don't need FreeBSD
definitions, like struct uuid(*)
o keep the original headers for compatibility, but rewrite them to
get the scheme definitions from <sys/disk/$scheme.h>.

(*) since UUID/GUID type definitions are non-portable and the GPT
scheme uses them, make it possible to have the scheme definitions
use an external type by allowing consumers of the header to set
GPT_UUID_TYPE. When GPT_UUID_TYPE has not been defined, the header
will use it's own type definition, which is the same as struct uuid.
The gpt_uuid_t typedef is created to abstract the details and allows
consumers to refer to a single type.

There is not conflict between the partitioning scheme headers and
what is defined in them. All headers can be included in the same
source files.

Note: consumers of the old headers have not been changed yet. Such
will be done if and when needed/beneficial.

Reviewed by: imp, jhb
MFC after: 1 month
Sponsored by: Bracket Computing