Bump libkdb5 API and DAL versions

We made two sets of incompatible changes to the DAL and libkdb5 API
during development for 1.11 (master key list simplification and policy
extensions), so increment the appropriate version numbers.
Set pointers to NULL after freeing them
Disconnect the texinfo users guide from the build

Its content has been migrated to or superseded by the krb_users
reST documentation.

The texinfo document attempted to have a general introduction to
Kerberos, but it is not quite suitable for the target audience
of the user's guide and will be rewritten.

A few portions of the texinfo document are simply no longer relevant
and do not need to be migrated.  In particular:
The krb5-appl utilities are out of scope for this document, as they
have been moved to a separate repository.  Coverage of ksu may be
brought back at a later time, though.
The Kerberos Glossary will be expanded and handled separately.

ticket: 7408
Remove make glue for texinfo users guide

Towards removing the texinfo docs entirely.

ticket: 7408
Remove unused texinfo sources

Now that the users guide make rules are removed, some of the texinfo
sources are not referenced from anywhere and can be safely removed.

ticket: 7408
Remove texinfo implementors guide

It is sufficiently old and unloved that nothing in it should be
taken as truth without independent verification.
Content of this nature should live on k5wiki.kerberos.org
in the future.

ticket: 7408
Add notice.rst

To replace the texinfo sources previously used to generate NOTICE.

When compiled to HTML, compares well against the original NOTICE.
Make rules for restructuredtext NOTICE file

Sphinx-build wants to scan over all the sources in the source dir,
and its text output engine does not handle the spanning row cells
used in some of our fancy tables, so it will crash if we attempt
to generate text output from our full suite of documents.
We could work around this by attempting to just compile the one
source file as an additional argument to sphinx-build, but this
seems to insist on producing an index.txt as well as a notice.txt.
Furthermore, we cannot use the same conf.py as in rst_composite because
the paths substitutions are not available with just the minimal
contents in the tree.

We use the standard |copy| macro from isonum.txt to get the unicode
codepoint if used for an HTML build, but prefer to just use the
literal ASCII "(C)" for text output.
Remove the last vestiges of the texinfo docs

We needed these last stragglers to build the NOTICE file at the
root of the tree, but we now generate a notice.txt from reST.

Man pages have been generated from reST for some time now, we no
longer need scripts to turn them into HTML and ps, as those can
be generated directly from the reST source.

The Makefile only existed to serve the texinfo builds, so it goes
away, too.  (The tgz target appears to have been broken since 1996.)

ticket: 7408
Remove stale implement document

As with the texinfo implementor's guide, it is sufficiently stale
so as to be untrustworthy without verification.
Content of this nature should live on k5wiki.kerberos.org.
Massive reST content rename

All of rst_source/ is now just in doc/.
The krb_ prefix is stripped from the document sub-directories.

ticket: 7409
Makefile update for RST move/rename
Update reST sources for mass rename