Apply a better fix for HitTest failures in the tests with GTK3

The actual cause of the problem was the tests making the single-line
text control height far too large. So just use the default height for
single-line controls.

src/gtk/textctrl.cpp

@@ -1582,17 +1582,7 @@ wxTextCtrl::HitTest(const wxPoint& pt, long *pos) const
         gtk_entry_get_layout_offsets(GTK_ENTRY(m_text), &ofsX, &ofsY);
 
         x -= ofsX;
-
-        // There is something really weird going on with vertical offset under
-        // GTK 3: normally it is just 0, because a single line control doesn't
-        // scroll vertically anyhow, but sometimes it can have big positive or
-        // negative values after scrolling horizontally, resulting in test
-        // failures in TextCtrlTestCase::HitTestSingleLine::Scrolled. So just
-        // ignore it completely, as, again, it shouldn't matter for single line
-        // text controls in any case, and so do not do this:
-#ifndef __WXGTK3__
         y -= ofsY;
-#endif // !__WXGTK3__
 
         // And scale the coordinates for Pango.
         x *= PANGO_SCALE;

tests/controls/textctrltest.cpp

@@ -166,14 +166,16 @@ long TextCtrlTestCase::ms_style = 0;
 
 void TextCtrlTestCase::CreateText(long extraStyles)
 {
+    const long style = ms_style | extraStyles;
+    const int h = (style & wxTE_MULTILINE) ? TEXT_HEIGHT : -1;
     m_text = new wxTextCtrl(wxTheApp->GetTopWindow(), wxID_ANY, "",
-                            wxDefaultPosition, wxSize(400, TEXT_HEIGHT),
+                            wxDefaultPosition, wxSize(400, h),
-                            ms_style | extraStyles);
+                            style);
 }
 
 void TextCtrlTestCase::setUp()
 {
-    CreateText(ms_style);
+    CreateText(0);
 }
 
 void TextCtrlTestCase::tearDown()