Thu, 07 Jun 2018 13:45:35 +0300Add retain basic implementation on GNU/Linux
Andrey Skvortsov <andrej.skvortzov@gmail.com> [Thu, 07 Jun 2018 13:45:35 +0300] rev 2173
Add retain basic implementation on GNU/Linux

Retain is saved in file and backup of this file is done every time.
File isn't saved on every PLC cycle to avoid high I/O load.
By default, retain is saved every second and on PLC stop/shutdown.
It's possible to override retain flush period by using CFLAGS option
in project's settings. For example, for 0.5 seconds period
use "-DFILE_RETAIN_SAVE_PERIOD_S=0.5".

Fri, 01 Jun 2018 15:46:17 +0300Add helper function GetRetainSize()
Andrey Skvortsov <andrej.skvortzov@gmail.com> [Fri, 01 Jun 2018 15:46:17 +0300] rev 2172
Add helper function GetRetainSize()

it will be useful for retain implementations.