Win: Use wxTE_NOHIDESEL for translation controls

Fixes drawing problems when setting selection programatically.

Fixes invisible highlighting of search results from Find.

Fixes #334.

Alternative fix for this, if it ends up causing problems, would be to:

1. override SelectAll() in AnyTranslatableTextCtrl to use
   wxWindowUpdateLocker before calling base class' implementation
   (bypasses the redrawing-problematic code in wxMSW).

2. Use syntax highlighting (e.g. yellow background) for find results
   instead of using selection (solves the problem of selection not being
   shown if Find window has focus).

src/text_control.h

@@ -46,7 +46,7 @@
 class CustomizedTextCtrl : public wxTextCtrl
 {
 public:
-    static const int ALWAYS_USED_STYLE = wxTE_MULTILINE | wxTE_RICH2;
+    static const int ALWAYS_USED_STYLE = wxTE_MULTILINE | wxTE_RICH2 | wxTE_NOHIDESEL;
 
     CustomizedTextCtrl(wxWindow *parent, wxWindowID winid, long style = 0);