Add deprecation test for readWriteThis methods

Signed-off-by: Ben Harshbarger <ben.harshb@gmail.com>

test/deprecated/IO/readWriteThis.chpl

@@ -0,0 +1,50 @@
+
+use IO;
+
+record A {
+  var x : int;
+
+  proc readWriteThis(f) {
+    if f.writing then f.write(x);
+    else f.read(x);
+  }
+}
+
+record B {
+  var y : real;
+}
+
+proc B.readWriteThis(f) {
+  if f.writing then f.write(y);
+  else f.read(y);
+}
+
+proc main() {
+  var f = openmem();
+  {
+    var w = f.writer();
+    var a = new A(42);
+    var b = new B(100);
+    w.writeln(a);
+    w.writeln(b);
+  }
+  {
+    var r = f.reader();
+    var contents : string;
+    r.readstring(contents);
+    writeln("===== Wrote: =====");
+    writeln(contents);
+    writeln("==================");
+  }
+  {
+    var r = f.reader();
+    var a : A;
+    var b : B;
+    r.readln(a);
+    r.readln(b);
+    writeln("===== Got: =====");
+    writeln(a);
+    writeln(b);
+    writeln("================");
+  }
+}

test/deprecated/IO/readWriteThis.good

@@ -0,0 +1,11 @@
+readWriteThis.chpl:7: warning: 'readWriteThis' methods are deprecated. Use 'readThis' and 'writeThis' methods instead.
+readWriteThis.chpl:17: warning: 'readWriteThis' methods are deprecated. Use 'readThis' and 'writeThis' methods instead.
+===== Wrote: =====
+42
+100.0
+
+==================
+===== Got: =====
+42
+100.0
+================