Disable TextCtrlTestCase::LongText() for non-MSW platforms.

At least under GTK SetMaxLength(), tested by this test, can't be used with
multiline text controls at all, so running it fails. Keep the test for MSW
only where SetMaxLength() works with controls of all kinds.

tests/controls/textctrltest.cpp

@@ -525,6 +525,9 @@ void TextCtrlTestCase::LogTextCtrl()
 
 void TextCtrlTestCase::LongText()
 {
+    // This test is only possible under MSW as in the other ports
+    // SetMaxLength() can't be used with multi line text controls.
+#ifdef __WXMSW__
     delete m_text;
     CreateText(wxTE_MULTILINE|wxTE_DONTWRAP);
 
@@ -554,6 +557,7 @@ void TextCtrlTestCase::LongText()
         wxString line = m_text->GetLineText(i);
         CPPUNIT_ASSERT_EQUAL( line, pattern );
     }
+#endif // __WXMSW__
 }
 
 void TextCtrlTestCase::PositionToCoords()