Add support for MSW unique volume names to wxFileName.

Recognize the paths starting with "\\?\Volume{GUID}" under MSW and provide a
way to test for them.

Closes #8874.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@62782 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/filename.h

@@ -433,6 +433,11 @@ public:
     // is the char a path separator for this format?
     static bool IsPathSeparator(wxChar ch, wxPathFormat format = wxPATH_NATIVE);
 
+    // is this is a DOS path which beings with a windows unique volume name
+    // ('\\?\Volume{guid}\')?
+    static bool IsMSWUniqueVolumeNamePath(const wxString& path,
+                                          wxPathFormat format = wxPATH_NATIVE);
+
     // Dir accessors
     size_t GetDirCount() const { return m_dirs.size(); }
     void AppendDir(const wxString& dir);