Enable wxCSConv UTF-7 test under Windows.

Even though it doesn't work with iconv under Unix, we can still enable this
test under Windows.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76407 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/strings/unicode.cpp

@@ -328,8 +328,9 @@ void UnicodeTestCase::ConversionUTF7()
         //    fine, go figure)
         //
         // I have no idea how to fix this so just disable the test for now
-#if 0
+#ifdef __WINDOWS__
-        d.Test(n, wxCSConv("utf-7"));
+        wxCSConv conv("utf-7");
+        d.Test(n, conv);
 #endif
         d.Test(n, wxConvUTF7);
     }