classes: Add a check that arguments to classoids are themselves classoids.
Introduce a new word-prop that makes tuple-class words classoids at parse-time so that
self-referential tuple definitions with maybe{} work, e.g. TUPLE: node { next maybe{ node } } ;
Add unit test.
Fixes #766.
sequences: require non-negative-integer for iotas.
hash-sets: faster M\ hash-set union.
Revert "hash-sets: faster M\ hash-set union."

This reverts commit bb7a1017f523a4e81b2aee041bd627b3484e65d7.
grouping: Remove <groups>, old <sliced-groups> is now <groups>. Fixes
grouping: Remove <clumps> and <circular-clumps> and rename <sliced-clumps>
and <sliced-circular-clumps> to those. Fixes #765.
basis/extra: Update last usages of <sliced-groups> to <groups>.
Configs: CFLAGS isn't used by the GNUMakefile, change it to SITE_CFLAGS.
Config.macosx: Add commented-out compiler flag to use 10.6.
See http://developer.apple.com/library/mac/#technotes/tn2064/_index.html
benchmark.reverse-complement: Fix usage of <groups>.
classes.union: Disallow unions to refer to themselves. Fixes #420 lol. Thanks @mrjbq7 for the patch.
benchmark.knucleotide: Fix usage of <clumps>.
splitting: Support SBUF" " with split-lines. Fixes #575. Thanks @mrjbq7
for the patch.
sorting: move push-unsafe and push-all-unsafe to growable.private.
hash-sets: speed up union on two hash-sets.
growable: use fixnum+fast and integer>fixnum.
sets: use push-unsafe in pruned.
assocs: Add of and ?of. Change all the things at once! Fixes #701.
classes.union: Fix circular reference between multiple definitions. Fixes #420 lol again.
Could be cleaner perhaps? I'm not seeing how right now.
assocs: tweak docs for new-assoc.