Support creating Unix wxUILocale for languages without region

Unlike MSW and macOS, creating wxUILocale for e.g. "en" doesn't
necessarily succeed under Linux even if "en_US" is available, so try to
find a working language+region combination if just language doesn't
work.

This requires access to the languages database, so add a private
wxGetLanguageInfos() to avoid having to depend on wxLocale just for
this.

src/common/intl.cpp

@@ -51,7 +51,8 @@
 #include "wx/stdpaths.h"
 #include "wx/hashset.h"
 #include "wx/uilocale.h"
-#include "wx/vector.h"
+
+#include "wx/private/uilocale.h"
 
 #ifdef __WIN32__
     #include "wx/msw/private/uilocale.h"
@@ -193,9 +194,16 @@ wxString wxLanguageInfo::GetLocaleName() const
 // wxLocale
 // ----------------------------------------------------------------------------
 
-static wxVector<wxLanguageInfo> gs_languagesDB;
+static wxLanguageInfos gs_languagesDB;
 static bool gs_languagesDBInitialized = false;
 
+const wxLanguageInfos& wxGetLanguageInfos()
+{
+    wxLocale::CreateLanguagesDB();
+
+    return gs_languagesDB;
+}
+
 /*static*/ void wxLocale::CreateLanguagesDB()
 {
     if (!gs_languagesDBInitialized)