KT-610 Distinguish errors 'unused variable' and 'variable is assigned but never accessed'

idea/src/org/jetbrains/jet/plugin/annotations/JetPsiChecker.java

@@ -88,7 +88,7 @@ public class JetPsiChecker implements Annotator {
                         }
                         else if (diagnostic.getSeverity() == Severity.WARNING) {
                             annotation = holder.createWarningAnnotation(diagnostic.getFactory().getTextRange(diagnostic), getMessage(diagnostic));
-                            if (diagnostic.getFactory() == Errors.UNUSED_VARIABLE) {
+                            if (diagnostic.getFactory() == Errors.UNUSED_VARIABLE || diagnostic.getFactory() == Errors.ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE) {
                                 annotation.setHighlightType(ProblemHighlightType.LIKE_UNUSED_SYMBOL);
                             }
                         }

idea/testData/checker/BinaryCallsOnNullableValues.jet

@@ -11,7 +11,7 @@ class C() {
 }
 
 fun f(): Unit {
-  var x: Int? = 1
+  var <warning>x</warning>: Int? = 1
   x = 1
   x <error>+</error> 1
   x <error>plus</error> 1