layours.hpp: Don't need RETAG here. Found by @mrjbq7. Fixes #637.
db, db.sqlite: If we are in a transaction, don't start another transaction. Add a unit test. Fixes #631. Fixes #623.
debugger: Fix error message.
core-foundation.numbers: support converting CFNumber back to factor.
ui.backend.cocoa.views: more robust respondsToSelector: (thanks @jckarter).