Make calling a constructor without new nor ending . canon

[cgrand]

In Dart, new has been deprecated and their notion of constructor is wide as they have:

• default constructor
• named constructors (to palliate the lack of overloads)
• const (interning) constructors
• factory constructors -- which are not even constructors any more IMO

So it's unclear when in ClojureDart . or new should be required and it adds little value (except potentially making some cljc works).

Thus I propose making officially new and ending . optional.

It's happens to already work but these codepaths should be checked to really work (especially w/ regards to type inference).

[cgrand]

(List) expands to (new List) here

ClojureDart/clj/src/cljd/compiler.cljc

Line 1002 in a1d35f3

:class (fn [form _ & _] (with-meta (cons 'new form) (meta form)))

(List/empty :growable true) expands to (. $lib:dc/List empty :growable true) which is then gantlet by emit-dot which has correct support for constructors:

ClojureDart/clj/src/cljd/compiler.cljc

Lines 1452 to 1453 in a1d35f3

	_ (when (and static (not (or (:static member-info) (= :constructor (:kind member-info)))))
	(throw (Exception. (str member-name " is neither a constructor nor a static member of " (:element-name type!)))))

ClojureDart/clj/src/cljd/compiler.cljc

Lines 1470 to 1472 in a1d35f3

	prop (case (:kind member-info)
	:field true
	(nil :method :constructor) prop)

ClojureDart/clj/src/cljd/compiler.cljc

Line 1478 in a1d35f3

(not prop) (:return-type member-info)

So all paths are clear!