Get $var.++ and $var.() working.

$var.:<++> etc is also parsed now, but is not functional.
[autounfudge] do not unfudge rakudo.parrot fudges on JVM, or vice versa
Make Any.exists|delete only work on undefined values
Remove exist_key and delete_key: they are not specced and not used in core
Hide Set|Bag.delete from backtrace, no point in showing exception from within
Add KeyBag|KeySet.delete, so that :delete works on KeyBag|KeySet
Simplify KeySet.exists: if a keys exists with value 0, we have a bug!
Simplify KeyBag|KeySet.at_key
Attempt to call a dotty prefix
Merge https://github.com/rakudo/rakudo into dottypost

Conflicts:
	src/Perl6/Actions.nqp
        (from attempts to .:<prefix> working)