Add missing testcase.

From-SVN: r205530

gcc/testsuite/g++.dg/torture/pr59208.C

+// { dg-do compile }
+class A {
+public:
+  A();
+  A(int *);
+};
+class B {};
+class C : B {
+public:
+  virtual void m_fn1();
+  void operator+=(int) { m_fn1(); }
+};
+enum DebuggerType {};
+C a;
+DebuggerType b;
+void operator==(A &, const A &);
+static A get_dbx_doc(A &p1) { p1 == 0; }
+
+void add_button() {
+  A c;
+  switch (b)
+  case 0:
+  get_dbx_doc(c);
+  a += 0;
+}