freopen: reset stream orientation (byte/wide) and encoding rule

freopen: reset stream orientation (byte/wide) and encoding rule

this is a requirement of the C language (orientation) and POSIX
(encoding rule) that was somehow overlooked.

we rely on the fact that the buffer pointers have been reset by
fflush, so that any future stdio operations on the stream will go
through the same code paths they would on a newly-opened file without
an orientation set, thereby setting the orientation as they should.