change exponential realloc algorithm on encoding and string decoding to be really exponential (this helps slow/debugging allocators such as libumem) (reported by Matthew Horsfall).
string encoding would needlessly overallocate output space (testcase by Matthew Horsfall).
be very paranoid about extending buffer lengths and croak if buffers get too large, which might (or might not) improve security.
add cbor-packed type to json_xs.
switch from YAML to YAML::XS in json_xs, as YAML is way too buggy and outdated.