Debian: CVE-2017-16872: pjproject -- security update

An issue was discovered in Teluu pjproject (pjlib and pjlib-util) in PJSIP before 2.7.1. Parsing the numeric header fields in a SIP message (like cseq, ttl, port, etc.) all had the potential to overflow, either causing unintended values to be captured or, if the values were subsequently converted back to strings, a buffer overrun. This will lead to a potential exploit using carefully crafted invalid values.