1st attempt to clean OS/2 support

[Miyata Shigeru]

I haven't modified my code to use traits as suggested by
Lars.  However it seems to work all right.
Please take a look, comment, critisize, and help me write
a clean code.  Please do not apply every thing blindly.

BTW I had to modify the type of BufferView::Pimpl::Position::par_pos
from int to LyXParagraph::size_type in order to compile here.

Regards,
                SMiyata

os_specific.diff.gz

os_specific.tar.gz