WIP: Add skeleton for MQTT extension based on part of OPC-UA extension.

For now generated code makes no sense but persistently-configurable-C-generating-extension infrastructure is there.

Merge remote-tracking branch 'origin/python3' into python3

C runtime: Fix PLCObject.hpp preventing build.

IDE: generalize EVT_GRID_CELL_CHANG{ING->ED} (WxPy4)

IDE: hopefully last fix about float type being passed to WxPy4.

IDE: enhance variable forcing contextual menu

IDE: fix completion

uses ctrl key on Mac
update internal variable list before listing them
avoid exception if empty list
apply selection when pressing return or enter

IDE: Workaround some reported WxPython/MacOS problems.

SetSelection should be used instead of SetStringSelection , and FindString must use case_sensitive=True

IDE: Fix search result not showing single occurrences

IDE: remove warning if editing location leads to no change

IDE: Use 8x8 grid by default

IDE: Fix exception when connecting complex types

LocalRuntime: no crash if zombie PLC prevents erasing workdir

IDE: Fix printing

More side effects of WxPy4 et Py3 + workaround WxWidget bug.

IDE: failsafe escaping for input not matching utf-8 encoding

Update Nevow revision in requirements.txt

Merge commit '2d061a66ddc737f5dffae82413b4f8573b7eee54' into HEAD

Add "CONTINUE" ST statement.

Matches "Add CONTINUE statement, fix FOR loop accordingly" 8a06b3bb92967b389466b8afa977a995ec605e2d commit in Matiec.

C runtime: cosmetic changes

merge again

Revert unwanted changes potentially breaking wxGlade support.
Partly revert 34d4c77ccb1bcb14601ab347ec6080466b7e143d. Skips evaluator related changes that was included by mistake.

Tests: add erpc source to GitHub tests

C runtime: add autoload

C runtime: fix logging, makes test pass

Tests: Add minimal C runtime test

merge

Xenomai runtime: report and mitigate when PLC cycle overruns.

Side effect :
_Log* macro was changed in plc_Xenomai_main.c,
and fixed in plc_Linux_main.c

SVGHMI: Do not generate Popen call when comamn is empty.

Fix python path in readme.

Python runtime: ensure that python thread finished before returning from StopPLC.

C runtime: initial fixes. Now runs and traces first_steps example.

beremiz_runtime -v -t tcp -p 61131 -h localhost

IDE: fix eRPC exception handling