#79 Allow non-ASCII install path on MS-Windows

[Hiroshi Yoshikawa]

This patch allows pkg-install-path to include non-ASCII characters on MS-Windows.
gerbv.exe can find essential files if the directory structure is like below:

<pkg-install-path> -+- bin\ -+- gerbv.exe
                    |        |
                    |        +- *.dll
                    |
                    +- lib\ -+- gdk-pixbuf-2.0\ - 2.10.0\ - loaders\ - lib*.dll
                    |        |
                    |        +- gtk-2.0\ -+- 2.10.0\ - engines\ - lib*.dll
                    |                     |
                    |                     +- modules\ - libgail.dll
                    |
                    +- share\ -+- gerbv\ - scheme\ - init.scm
                               |
                               +- locale\ - <lang> - LC_MESSAGES\ - gerbv.mo
                               |
                               +- themes\ - MS-Windows\ - gtk-2.0\ - gtkrc