Check presence of dispatch receiver parameter in modifier checks

Also fix typo in "inapplicable infix" diagnostic message

idea/testData/intentions/toInfixCall/singlePackageFunctionCall.kt

@@ -1,6 +1,6 @@
 // WITH_RUNTIME
 // IS_APPLICABLE: false
-// ERROR: 'infix' modifier is inapplicable on this function: must be a member of an extension function
+// ERROR: 'infix' modifier is inapplicable on this function: must be a member or an extension function
 
 package demo
 
@@ -8,4 +8,4 @@ infix fun foo(str: String) = kotlin.io.println(str)
 
 fun main() {
     <caret>demo.foo("")
-}
+}