Merge pull request #210 from Mouq/nom

Allow #`[space] in regexes (Unrelated to RT#77522)
Move empty set symbol to right place, but alas still doesn't work
Add empty set as a term.  Not sure how to go on from here, though  :-(
Add Action for empty set
use nqp's unlink, rather than parrot's
bump nqp revision
Mark all .delete methods as DEPRECATED, add delete_key|pos methods as needed
Change all calls to '.delete' to .delete_key|pos
Make sure [3,*-3]:delete works
bump NQP revision

because we can.
Make Pair.invert return a Pair, rather than an Enum

(or anything else that inherits from Enum)
Make sure delete attempts past end of array doesn't vivify
Added method "invert" to Baggy, as per TimToady's mumbling
Moved method .chrs from Iterable to Cool, as per other TimToady mumbling
Make sure @a:exists and @a:delete tests are run