buildroot

libpjsip: security bump to 2.7.2

Fixes the following vulnerabilities:

- CVE-2018-1000098: Crash when parsing SDP with an invalid media format
  description

- CVE-2018-1000099: Crash when receiving SDP with invalid fmtp attribute

[Peter: add CVE info]
Signed-off-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

(cherry picked from commit ed0d9d6f36dfc3e99ee70cc34de0c380925e871f)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>