CBOR text gets truncated on decoding

[sugmanue]

There are two bugs in the _finishLongTextAscii method introduced in #519 that produces the text to be truncated.

1. The outPtr is always set to zero (see here) before the read loop. If the out buffer still has room its contents will be overwritten instead of keep adding to it (overwrite or missing chunks.)
2. If the method exits by fully reading the expected text length, outside the outer loop the length of the last segment is not set, which makes the calling code to drop it when the string is finished (text truncated.)

[sugmanue]

#617 fixes the issues described in this issue. This is, unfortunately a data loss bug and thus critical, let me know if there's anything else that is needed.