Extract static functions to CodegenTestUtil

Add Nullable/NotNull annotations

compiler/tests/org/jetbrains/jet/codegen/PatternMatchingTest.java

@@ -16,10 +16,13 @@
 
 package org.jetbrains.jet.codegen;
 
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.ConfigurationKind;
 
 import java.lang.reflect.Method;
 
+import static org.jetbrains.jet.codegen.CodegenTestUtil.assertThrows;
+
 public class PatternMatchingTest extends CodegenTestCase {
     @Override
     protected void setUp() throws Exception {
@@ -27,6 +30,7 @@ public class PatternMatchingTest extends CodegenTestCase {
         createEnvironmentWithMockJdkAndIdeaAnnotations(ConfigurationKind.JDK_ONLY);
     }
 
+    @NotNull
     @Override
     protected String getPrefix() {
         return "patternMatching";