Make _() and friends safe to call from any thread.

The GetUntranslatedString() hack keeps a global copy of all strings, so
that it can return a const reference as wxGetTranslation() return value.
A global wxHashSet instance shared by all threads won't do, even guarded
with a critical section, because it may internally copy values on any
insert and thus invalidate pointers that may still be used on another
thread.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74833 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/private/threadinfo.h

@@ -14,6 +14,13 @@
 
 class WXDLLIMPEXP_FWD_BASE wxLog;
 
+#if wxUSE_INTL
+#include "wx/hashset.h"
+WX_DECLARE_HASH_SET(wxString, wxStringHash, wxStringEqual,
+                    wxLocaleUntranslatedStrings);
+#endif
+
+
 // ----------------------------------------------------------------------------
 // wxThreadSpecificInfo: contains all thread-specific information used by wx
 // ----------------------------------------------------------------------------
@@ -40,6 +47,11 @@ public:
     //     logging
     bool loggingDisabled;
 
+#if wxUSE_INTL
+    // Storage for wxTranslations::GetUntranslatedString()
+    wxLocaleUntranslatedStrings untranslatedStrings;
+#endif
+
 private:
     wxThreadSpecificInfo() : logger(NULL), loggingDisabled(false) {}
 };