Support for callable references in smart completion

idea/idea-completion/testData/handlers/smart/CallableReference3.kt

@@ -0,0 +1,9 @@
+fun foo(p: () -> Unit){}
+
+fun bar() {
+    foo(::<caret>)
+}
+
+fun f(){}
+
+// ELEMENT: f

idea/idea-completion/testData/handlers/smart/CallableReference3.kt.after

@@ -0,0 +1,9 @@
+fun foo(p: () -> Unit){}
+
+fun bar() {
+    foo(::f)<caret>
+}
+
+fun f(){}
+
+// ELEMENT: f

idea/idea-completion/testData/handlers/smart/CallableReference4.kt

@@ -0,0 +1,12 @@
+class C
+
+fun C.extFun(s: String){}
+
+fun foo(p: C.(String) -> Unit, c: Char){}
+fun foo(p: (String) -> Unit){}
+
+fun bar() {
+    foo(C::<caret>)
+}
+
+// ELEMENT: extFun

idea/idea-completion/testData/handlers/smart/CallableReference4.kt.after

@@ -0,0 +1,12 @@
+class C
+
+fun C.extFun(s: String){}
+
+fun foo(p: C.(String) -> Unit, c: Char){}
+fun foo(p: (String) -> Unit){}
+
+fun bar() {
+    foo(C::extFun, <caret>)
+}
+
+// ELEMENT: extFun