Bugfix Min max values for device data checks: Devicedata was set to it lower limit in case of a lower invalid value and upper limit in case a bigger value was detected. This could cause the history memory to be set to a min / max limit and never beeing updated again => Implemented a selection to specify which limit shall be used as default. Minor change: "header" was used as global as well as as local variable => changed name for global variant to gheader. Operation hours were not updated =>adde check for opeartion hours

Imported from Ac6/SystemWorkbench/plugins/fr.ac6.mcu.firmware_1.14.7.201711101414/resources/builtin/:
* File syscalls.c