Add tests on quick fix that adds 'actual' to platform declaration

#KT-18454

idea/testData/multiModuleQuickFix/addActualToClassMember/header/header.kt

@@ -0,0 +1,3 @@
+expect class Foo {
+    fun foo()
+}

idea/testData/multiModuleQuickFix/addActualToClassMember/header/header.kt.after

@@ -0,0 +1,3 @@
+expect class Foo {
+    fun foo()
+}