Fix off-by-one causing buffer overflow in open_memstream
Fix off-by-one causing buffer overflow in open_memstream

Fixes #140

Signed-off-by: phirsov <c6938fa957315fae607f5ae4464befa29d39c210@users.noreply.github.com>

intel/tinycbor,01org/tinycbor,intel/tinycbor,thiagomacieira/tinycbor,thiagomacieira/tinycbor,thiagomacieira/tinycbor,01org/tinycbor,intel/tinycbor,01org/tinycbor,intel/tinycbor,thiagomacieira/tinycbor