elm_prefs: compatibility for Windows.

Summary:
Add test for relative path on Windows

@fix

Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>

legacy/elementary/src/lib/elm_prefs.c

@@ -1146,7 +1146,11 @@ _elm_prefs_efl_file_file_set(Eo *obj, Elm_Prefs_Data *sd, const char *file, cons
      sd->file = eina_stringshare_printf("%s/%s", prefix, "preferences.epb");
    else
      {
+#ifndef _WIN32
         if (*file != '/') /* relative */
+#else
+        if (!(strchr(file,':'))) /* relative */
+#endif
           sd->file = eina_stringshare_printf("%s/%s", prefix, file);
         else
           sd->file = eina_stringshare_add(file);