Minor DJGPP fixes

[Laurynas Biveinis]

Zack Weinberg wrote:

> I'm now convinced that nonblocking open is more trouble than it's
> worth.  I've committed the following patch:
> 
>         * cppfiles.c (open_include_file): Open file in blocking mode.
>         (read_include_file): Don't fcntl(fd, F_SETFL, 0) anymore.
>         Only exclude block devices and directories.
> 
> Please let me know if it doesn't fix your problem.

Yes it does, thanks.
Laurynas Biveinis