Port various documentation topics to xdoc.
start of tour stuff and doc updates
second recovered patch from old git
fix autohide bug
port documentation for easy-simplify to xdoc
port untranslate-patterns documentation to xdoc
Merge remote-tracking branch 'remotes/origin/master' into doc
probably broken commit to work on data-structures docs
Merge remote-tracking branch 'remotes/origin/master' into doc
better cleaning of quicklisp, port data-structures docs to xdoc
port memory library documentation to xdoc
port some ihs documentation to xdoc
merge doc branch with master
merge master into doc

abandon effort to move tours into their own package, for now at least,
to avoid conflicts
minor markup changes to acl2-doc.lisp

Mostly this is to avoid strings of equal signs, to make it
slightly easier to merge conflicts.
switch xdoc files to camelCase for consistency
more documentation work on logops-lemmas.
blah more docs
minor efficiency boosts to ihs basic-definitions (loghead mostly)
merge basic-definitions updates