Fix a bug in chaining multiple notins after a join.

Somewhat obscure, but arises in RSE/GC-generated code. Basic problem is that we
only want to call setup_accessors once; for lefts/rights, we were calling it
multiple times. Unclear why that mucked things up, but it was certainly wrong
anyway.

On examination, the code for assigning a schema to a pairs join is completely
bogus anyway (see comment) -- but I won't fix that for now.
Tweak new notin test case.
Merge branch 'master' into gc-proto-v1
Fix minor bug in JoinInfoParser.
Tweak RSE for self joins.

Now that the bug with chaining multiple notins after a join has been fixed, we
can generate simpler Bloom rules for reclamation.