Single-branch if-statements

Single-branch if-expressions are now compiled to statements if the result is
not used

 #KT-3036 In Progress

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

@@ -295,6 +295,10 @@ public class LineNumberTest extends TestCaseWithTmpdir {
         doTest();
     }
 
+    public void testIfThen() {
+        doTestCustom();
+    }
+
     public void testStaticDelegate() {
         JetFile foo = createPsiFile("staticDelegate/foo.kt");
         JetFile bar = createPsiFile("staticDelegate/bar.kt");