sipp: buffer overflows in get_remote_ip_media() and get_remote_ipv6_media()

Multiple stack-based buffer overflows in the (1) get_remote_ip_media and (2) get_remote_ipv6_media functions in call.cpp in SIPp 3.1 allow remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via a crafted SIP message.