Dealing with infix calls in completion

#KT-4846 Fixed

idea/testData/completion/basic/common/InfixCall.kt

@@ -0,0 +1,33 @@
+class C {
+    fun foo(){}
+    fun bar(p: Int) {}
+    fun zoo(p1: Int, p2: Int){}
+    val prop: Int = 1
+}
+
+fun C.xxx() {}
+fun C.yyy(p: Int) {}
+fun C.zzz(p1: Int, p2: Int) {}
+val C.extensionProp: Int get() = 1
+
+fun <A, B> A.and(that: B): Pair<A, B> = Pair(this, that)
+
+fun String.ttt(p: Int) {}
+
+fun f() {
+    C() <caret>
+}
+
+// ABSENT: "foo"
+// EXIST: "bar"
+// ABSENT: "zoo"
+// ABSENT: "prop"
+
+// ABSENT: "xxx"
+// EXIST: "yyy"
+// ABSENT: "zzz"
+// ABSENT: "extensionProp"
+
+// EXIST: "and"
+
+// ABSENT: "ttt"