[Mono-list] making the windows path relative

[Miguel de Icaza]

Hello Johannes!

> I know, I've already asked this question some time ago, but I think it's
> important.
> I want to get the search path for the mono assemblies not fixed, but
> realative to the bin directory (e.g ../lib)

I have now implemented something that will look up the directory at
runtime based on the filename, but I need someone to test this for me,
as I do not run Mono on Windows.

I have also added a `mono/mono/os' directory, where we have currently
two things: `os/unix' and `os/win32', so we can put OS specific code
here instead of using #ifdef PLATFORM_WIN32 code all over the place. 

I will commit as soon as I try the code out in Linux, I would appreciate
if someone with Windows can give it a shot.

Best wishes,
Miguel.