Improve LIKE/regex handling.

* Move handling of LIKE patterns to the compiler,
* add a `Search` functinon that takes a regex,
* add support for Postgres’ `~` operator (alias for `Search`),
* enable escape characters for LIKE patterns (fixes #65),
* change parsing of “suffixes” to be less hacky, and
* get rid of the `NotIn` and `NotLike` Binops and std lib functions.
We should probably create an object here, e.g. `StdNames` and put all the hard-coded function names in there so it'll be easier to locate & change them. It's OK for the parser to do this translation on the fly for syntax sugar, it would just help if we make it a bit easier to figure out what's being hard coded.