Remove -- from doc-files.

Thanks to Andreas for pointing this out.

Delete trailing whitespace in help/Docfiles

Prim_rec: whitespace cleanup in both .sig and .doc

Purge on broken links within the (HTML) documentation. This mostly involves
deleting SEEALSO entries (where documentation doesn't exist) but also fixing a
few links.

Also fixed the anchor links in TheoryIndex.html and idIndex.html. In both
cases there aren't any entries starting with the letter "Y".

Removed a bunch of rarely used functions from hol88Lib. Related documentation
updated.

The ancient hol88 interface should disappear eventually; code using it should
be properly ported to use the current HOL functions instead.

Huge number of check-ins, implementing change to .doc file syntax.
Now the rule for text within braces is that it appears as given, but
that braces must balance. If you want an unbalanced brace, you can use
\lbrace or \rbrace. No existing .doc file uses unbalanced braces.
Also, there is now no need to use \noindent. In fact, doing so
will get you a complaint from the parser. Similarly, use of \ or
{} characters outside of verbatim text blocks will cause griping.
All of the new files have been generated by a parse-then-print process
from the old files, and it's possible there are errors. If you ever
have a spare moment, casting your eye over a random selection of these
might help to find errors.

Many fixups, most to do with braces not being doubled properly in a slew
of .doc files. Also, remember to provide an identifier after the
initial \DOC.

New versions of docfiles.