VL: add support for `define macros with arguments

This turns out to be pretty hideous.  Added a few systests to try
to test it.  Started toward extending VL systests to VCS instead of
just NCV, but that's probably not working yet.
fix bug with memoize tests
Updated SINCE in purity script to avoid irrelevant log issue.
Fixed multi-threading memoization issue reported by Jared and David.

Thanks to Jared, who supplied a really helpful example provoking the bug.
Turned on/off multithreading for memoization according to whether waterfall parallelism is turned on/off, as worked out with David Rager.
Installed final (?) patches to allow safe multi-threading in ACL2(hp).

What remains is, probably, to stop defeating memoization in ACL2(hp)
when waterfall-parallelism is enabled.  I've been in correspondence
with David Rager about a possible approach, which he might
investigate.

Note: I have not run regression on these changes, which should only
affect ACL2(p) and ACL2(hp) and have been discussed verbally with
David and Jared.  But I have built both of those as well as ACL2 and
ACL2(h), and run :mini-proveall tests in each.
Adding hons and hons-acons tests for the spec-mv-let system.

Also, cleaning up hons and hons-acons tests that used pand, since functions that use pand probably need their guards verified to actually use the parallelism system.

Fixes #279
Merge pull request #280 from ragerdl/master

Adding hons and hons-acons tests for the spec-mv-let system.
Removing a couple .acl2 files that are no longer necessary now that we support waterfall-parallelism with ACL2(hp) in a better way
Extend xdoc with resource directories for images or other files.
fix up edgesynth documentation for new resource directory stuff
VL: new (preliminary) hunchentoot-based module browser
extra .gitignore for centaur
Fixed bug pointed out by David Rager, which made SBCL builds fail for ACL2(hp).

I think the problem had to do with recent changes I've made involving
with-lock and (recently added) with-lock-raw.  The fix was to change
calls of with-lock in multi-threading-raw.lisp to with-lock-raw, since
with-lock is defined in axioms.lisp, which is loaded after
multi-threading-raw.lisp.  I'm a little surprised that this bug didn't
show up in CCL.  And, this is another case where I'm glad we support
multiple Lisps.

(Normally I run a full regression, but this change can only affect
ACL2(p) and ACL2(hp) and builds work fine, so checking in.)

Also, added a comment for state global acl2-sources-dir saying why it
should not be deleted (Jared now uses it for XDOC).
Merge remote-tracking branch 'upstream/master'
Undoing the removal of setting waterfall
parallelism to nil in a Milawa file since I was unable to build Milawa
and confirm that the removal was an okay thing to do.

@jaredcdavis you may want to build Milawa on a recent CCL when you
  have a chance -- I was getting an error about an invalid memory
  access (like what we get when we take the car of 3)
minor updates to vl pretty printing, to use scope stacks
add bt-semaphore quicklisp library, minor printing/scopestack fixes
minor documentation fixes
one last doc fix