[var] various upgrades to var:

* var is promoted to the main package.
* It is no longer an opt-in thing.
* bug: var (unlike val) is allowed in old-style for loops, but if you multi-init: for (var i = 0, j="Foo";;), you now get an error that you can't do that.
* tests both for the multi-for situation and the new main package variant.

test/transform/resource/before/VarInForOldMulti.java

@@ -0,0 +1,10 @@
+//skip compare contents
+import lombok.var;
+
+public class VarInForOldMulti {
+	public void oldForMulti() {
+		for (var i = 0, j = "Hey"; i < 100; ++i) {
+			System.out.println(i);
+		}
+	}
+}