Added :doc git-quick-start.  Updated :doc community-books for github.  Added static-hons support for GCL.  Use compiled memoized functions during include-book.  For Lisps that don't always compile, memoize only compiles when existing function is compiled.

:Doc note-7-0 has a link to new topic git-quick-start, and also says:

  Static honsing for ACL2(h), an efficiency enhancement formerly only
  available for CCL, is now incorporated into builds on sufficiently
  recent GCL versions.

  ACL2(h) could fail to use previously-compiled definitions for
  [memoize]d functions when [include-book] is invoked. This has been
  fixed.

  (For ACL2(h), and irrelevant for CCL and SBCL) Calls of [memoize]
  only compile the memoized definition when the original function is
  compiled, rather than unconditionally as before.

Also fixed a small bug in :doc note-7-0: @(tsee pbt!) should have been
@(tsee pcb!), and now it is.

NOTE regarding the new :doc topic, git-quick-start, in
books/system/doc/acl2-doc.lisp: I suspect that the pairs of
fetch/merge commands can be replaced by a suitable pull command.  If
anyone is SURE about that, I hope that person will make that change.
Merge remote-tracking branch 'remotes/origin/master'
Merge remote-tracking branch 'remotes/origin/master'