The current code in json_quote_str() only accepts strict printable ASCII
code points (i.e. 32-127), all other code points are dropped from the
JSON output. The code is attempting to drop only non-printable ASCII
characters, but doing a signed comparison of the byte value is also
dropping characters with values >= 128.
This patch uses an unsigned comparison to accept code points 32-255.
Reviewed-by: Carl Worth <cworth@cworth.org> (with some additional
details for commit message).
In the case of notmuch-show, "--format=json" also implies
"--entire-thread" as the thread structure is implicit in the emitted
document tree.
As a coincidence to the implementation, multipart message ID numbers are
now incremented with each part printed. This changes the previous
semantics, which were unclear and not necessary related to the actual
ordering of the message parts.
