Allow creating wxUILocale objects for any locale

Creating such objects (without using them for the UI) is supported under
all platforms, so allow doing it.

Note that this is only supported under Unix systems when locale_t and
related functionality is available, but this should be the case just
about everywhere by now.

Add a test (or, rather, replace an existing test which was disabled by
default) checking that we can now get locale information about any
locale, not necessarily the currently used one.

include/wx/private/uilocale.h

@@ -33,9 +33,17 @@ public:
     // It may return NULL in case of failure.
     static wxUILocaleImpl* CreateUserDefault();
 
+    // Create locale object for the given locale.
+    //
+    // It may return NULL in case of failure.
+    static wxUILocaleImpl* CreateForLocale(const wxLocaleIdent& locId);
+
     // This function exists only for wxLocale compatibility and creates the
     // locale corresponding to the given language.
     //
+    // It is implemented in terms of CreateForLocale() for non-MSW platforms,
+    // but under MSW it is different for compatibility reasons.
+    //
     // The language passed to this function is a valid language, i.e. neither
     // wxLANGUAGE_UNKNOWN nor wxLANGUAGE_DEFAULT.
     //