[MDC-421] add nic_simet2_simet-ma SIMET engine package

[MDC-421] add nic_simet2_simet-ma SIMET engine package

Add the new SIMET2 engine as the simetbox-openwrt-simet-ma package of
simetbox-openwrt-feed.

Add a procd-style OpenWRT initscript to call simetbox_register_ma.sh on
boot, and to handle the SIMET2 Internet Availability measurement client
(inetupc).  Direct procd to respawn the inetupc client if it crashes or
exits.

Use the uci-default run-once mechanism to add to the crontab a daily
cronjob that will refresh a missing/invalid/expired agent ticket and
agent-id.

Notes:
By default at least OpenWRT Chaos Calmer will attempt to do make
CC=<something>, etc.  And that will break the build in chaos calmer
(because we need the -std=gnu99 that AC_PROC_CC_STD added to CC).
Ensure it will do a plain make call to build, instead.  All proper flags
have been set at configure time.

Depend on flock when busybox is not providing flock, this happens on
OpenWRT Chaos Calmer.

Conditionally install /lib/simet and /etc/simet, so that we can have one
of them empty without breaking the build.  Ensure /etc/simet directory
will be created even if empty: we will need it there.