Enhance wxUILocale and wxLocaleIdent

Many improvements and fixes to wxUILocale:

- Add wxUILocale method for retrieving wxLocaleIdent identifier,
  localized names, layout direction.
- Add wxLocaleIdent attributes, getter, and setter for
  platform-dependent tags under Windows: extension, sort order.
- Modify method wxLocaleIdent::FromTag to support not only BCP 47-like
  tags, but also platform-dependent syntax.
- Modify method wxLocaleIdent::GetTag to allow specifying the tag type.
- Update internat sample to better show using wxUILocale.
- Update German and French message catalogs for internat sample (German
  fully translated, French msgIds only).
- Introduced wxUILocaleImplStdC under Windows, because locale "en-US" is
  not equivalent to the C locale.
- Adjust wxLocale class to restore previous wxUILocale in the
  destructor.
- Implement wxLocale::GetInfo method through wxUILocale methods.
- Removed LCID dependency in wxLocale.
- Move the implementation of some static wxUILocale methods from
  intl.cpp to uilocale.cpp.

Co-authored-by: Vadim Zeitlin <vadim@wxwidgets.org>

Closes #2615.

include/wx/localedefs.h

@@ -32,6 +32,31 @@ enum wxLayoutDirection
 // wxLocaleCategory: the category of locale settings
 // ----------------------------------------------------------------------------
 
+enum wxLocaleTagType
+{
+    // Default (tag as given or else same as wxLOCALE_TAGTYPE_SYSTEM)
+    wxLOCALE_TAGTYPE_DEFAULT,
+
+    // Default type of the system (platform-dependent)
+    wxLOCALE_TAGTYPE_SYSTEM,
+
+    // BCP47-like type: <language>[-<script>][-<region>][-<modifier>]
+    wxLOCALE_TAGTYPE_BCP47,
+
+    // macOS type: <language>[-<script>][_<region>]
+    wxLOCALE_TAGTYPE_MACOS,
+
+    // POSIX type: <language>_<region>[.<charset>][@{<scriptalias>|<modifier>}]
+    wxLOCALE_TAGTYPE_POSIX,
+
+    // Windows type:  <language>[-<script>][-<region>][-<extension>][_<sortorder>]
+    wxLOCALE_TAGTYPE_WINDOWS
+};
+
+// ----------------------------------------------------------------------------
+// wxLocaleCategory: the category of locale settings
+// ----------------------------------------------------------------------------
+
 enum wxLocaleCategory
 {
     // (any) numbers
@@ -74,6 +99,27 @@ enum wxLocaleInfo
 
 };
 
+// ----------------------------------------------------------------------------
+// wxLocaleName: the items understood by wxLocale::GetLocalizedName()
+// ----------------------------------------------------------------------------
+
+enum wxLocaleName
+{
+    wxLOCALE_NAME_LOCALE,
+    wxLOCALE_NAME_LANGUAGE,
+    wxLOCALE_NAME_COUNTRY
+};
+
+// ----------------------------------------------------------------------------
+// wxLocaleForm: the forms of names understood by wxLocale::GetLocalizedName()
+// ----------------------------------------------------------------------------
+
+enum wxLocaleForm
+{
+    wxLOCALE_FORM_NATIVE,
+    wxLOCALE_FORM_ENGLISH
+};
+
 // ----------------------------------------------------------------------------
 // wxLanguageInfo: encapsulates wxLanguage to OS native lang.desc.
 //                 translation information