Always use wxTE_MULTILINE explicitly in PositionToCoords() test

While it is added implicitly when running all tests in the order, this
style wasn't used if just this test was ran using "-c PositionToCoords"
option.

Specify wxTE_MULTILINE in it explicitly to allow this to work too.

tests/controls/textctrltest.cpp

@@ -603,7 +603,7 @@ void TextCtrlTestCase::PositionToCoordsRich2()
 void TextCtrlTestCase::DoPositionToCoordsTestWithStyle(long style)
 {
     delete m_text;
-    CreateText(style);
+    CreateText(style|wxTE_MULTILINE);
 
     // Asking for invalid index should fail.
     WX_ASSERT_FAILS_WITH_ASSERT( m_text->PositionToCoords(1) );