Add cbor_value_to_json_stream().

This is stream output API that similar to cbor_value_to_pretty_stream().
It makes easy handling to various output targets.

cbor_value_to_json_stream() is a generalized implementation of cbor_value_to_json_advance().
Replacing all fprintf() and fputs() used by internal functions with
CborStreamFunction to handle to various output targets.

cbor_value_to_json_advance() remake as a front-end for cbor_value_to_json_stream()
that specialized for FILE stream.

Signed-off-by: TOKITA, Hiroshi <tokita.hiroshi@gmail.com>

cbor_value_to_json_stream() calls cbor_value_to_pretty_stream() with the stream that given for it,
for output directly the text that representation of value.
It is no need to cache with memstream.

In map_to_json(), the map key may be written twice.
In such case, keeping iterator copy and use for re-read.

Signed-off-by: TOKITA, Hiroshi <tokita.hiroshi@gmail.com>

Using cbor_value_to_json_stream() and CborStreamFuction instead of open_memstream().

Signed-off-by: TOKITA, Hiroshi <tokita.hiroshi@gmail.com>

As a result of disappearing dependencies to open_memstream(),
MSVC got able to use "CBOR to JSON" APIs.

Add cbortojson.c to compile target and enable `tojson` tests.

Signed-off-by: TOKITA, Hiroshi <tokita.hiroshi@gmail.com>

Remove open_memstream.c and related configs that became unneeded with JSON stream API.

Signed-off-by: TOKITA, Hiroshi <tokita.hiroshi@gmail.com>