Using os.Path.pathType() on Windows

Before version 3.10, on Windows platforms, a filename starting with a directory-separator (slash or backslash) was not interpreted by os.Path.pathType() as an absolute name. As result, such files where considered as relative path and searched by concatenating the path to the elements defined in FGLLDPATH, FGLRESOURCEPATH, FGLIMAGEPATH.

Starting with version 3.10, a filename starting with a directory-separator or starting with a drive letter, is considered an absolute file path.

This change has also an impact on the os.Path.join method, which returns the second parameter only if it is identified as an absolute path.