Will call underlying C virtual methods of stream interface. This isn't
intended to be added to every stream object (it's not in CPython), but
is convenient way to expose extra operation on Python side without
adding bunch of Python-level methods.

Spools entire output buffer to a blocking stream (chunk by chunk if
needed).

This allows the mp_obj_t type to be configured to something other than a
pointer-sized primitive type.

This patch also includes additional changes to allow the code to compile
when sizeof(mp_uint_t) != sizeof(void*), such as using size_t instead of
mp_uint_t, and various casts.

Addresses issue #1022.

Also, implement for unix port.

Also, usocket.readinto(). Known issue is that .readinto() should be available
only for binary files, but micropython uses single method table for both
binary and text files.

Blanket wide to all .c and .h files.  Some files originating from ST are
difficult to deal with (license wise) so it was left out of those.

Also merged modpyb.h, modos.h, modstm.h and modtime.h in stmhal/.

Uses stream_unbuffered_readline underline.

These can be used for any object which implements stream protocol
(mp_stream_p_t).