[gexiv2] gioio: implement wpath() to fix build on Windows

[Jens Georg <jensgeorg src gnome org>]

commit 9f0e0b985eeeabd60aab236f99eb104927578253
Author: Christoph Reiter <reiter christoph gmail com>
Date:   Mon Jun 3 08:18:17 2019 +0200

    gioio: implement wpath() to fix build on Windows
    
    On Windows the BasicIo class has an additional pure virtual function
    called wpath() guarded by EXV_UNICODE_PATH.
    
    GioIo was missing an implementation and that made the build fail on Windows.
    
    Fixes #41

 gexiv2/gexiv2-metadata.cpp | 9 +++++++++
 1 file changed, 9 insertions(+)
---
diff --git a/gexiv2/gexiv2-metadata.cpp b/gexiv2/gexiv2-metadata.cpp
index ab8e091..fb32a6b 100644
--- a/gexiv2/gexiv2-metadata.cpp
+++ b/gexiv2/gexiv2-metadata.cpp
@@ -206,6 +206,15 @@ public:
         return "GIO Wrapper";
     }
 
+#ifdef EXV_UNICODE_PATH
+    std::wstring wpath() const {
+        std::string p = path();
+        std::wstring w(p.length(), L' ');
+        std::copy(p.begin(), p.end(), w.begin());
+        return w;
+    }
+#endif
+
 #if EXIV2_TEST_VERSION(0,27,99)
     Exiv2::BasicIo::UniquePtr temporary() const {
         return Exiv2::BasicIo::UniquePtr(nullptr);