Linux runtime: overrun detection for real-time timers and for plc execution.

If real-time timer wakes-up PLC thread too late (10% over period), then
warning is logged.

If PLC code (IO retreive, execution, IO publish) takes longer than requested
PLC execution cycle, then warning is logged, and CPU hoogging is mitigated
by delaying next PLC execution a few cylces more until having at least
1ms minimal idle time.

#
# Dockerfile for wxPython3.0 running on python2.7
#

FROM python:2.7-stretch

RUN set -xe \
    && apt-get update \
    && apt-get install -y --no-install-recommends python-wxgtk3.0 python-matplotlib \
    && apt-get install -y --no-install-recommends python-xvfbwrapper xvfb \
    && apt-get clean