Move property to constructor preserves vararg keyword (#1095)

#KT-18035 Fixed

idea/testData/quickfix/canBePrimaryConstructorProperty/vararg.kt

@@ -0,0 +1,4 @@
+// "Move to constructor" "true"
+class A(vararg strings: String) {
+    val <caret>strings = strings
+}

idea/testData/quickfix/canBePrimaryConstructorProperty/vararg.kt.after

@@ -0,0 +1,3 @@
+// "Move to constructor" "true"
+class A(vararg val strings: String) {
+}