prevent PRI underflow
Merge branch 'v5.8.6-prifix' into v5.8.13-prifix
Merge branch 'v5.8.13-prifix' into v5-stable-prifix
Merge branch 'v5-stable-prifix' into v7-stable-prifix
invalid facilities: include full rawmsg in MSG property

Based on RFC3164 definitions, this makes a lot of sense. Thanks to
mancha for suggesting this behaviour.
cleanup: remove comment that no longer applies
do not try to parse messages with invalid facility (RFC3164 mode)
parser: do not unnecessarily parse invalid PRI

abort as soon as we know its too high
testbench: add invalid facility tests
prepare for 7.6.7
fix build problem on some platforms