Add more tests

Author: nicolasstucki

tests/neg-custom-args/fatal-warnings/i5013b.scala

@@ -0,0 +1,16 @@
+class Foo {
+
+  val a: Int = 3
+
+  def b: 1 = {
+    println("1")
+    1
+  }
+
+  val c: Unit = ()
+
+  def foo1: Unit = a // error: A pure expression does nothing in statement position
+  def foo2: Unit = b
+  def foo3: Unit = c // Not addapted to { c; () } and hence c is not a statement
+
+}