testing/mqtt-exec: new aport

simple MQTT client that executes a command on messages
https://github.com/ncopa/mqtt-exec
main/libpcap: upgrade to 1.5.1
main/serf: upgrade to 1.3.2
testing/aports-build: new aports

MQTT based build-on-git-push scripts
main/qemu: upgrade to 1.7.0
main/gcc: update fix to compile Ada with -fno-stack-check.
testing/aports-build: send msg to irc on failure