SVGHMI: optimization of C part : stop traversing the whole HMI tree, use dual linked list for subscriptions and single linked list for changes from HMI. Intermediate commit, still crashing in some cases.

<?xml version='1.0' encoding='utf-8'?>
<BaseParams xmlns:xsd="http://www.w3.org/2001/XMLSchema" IEC_Channel="1" Name="ModbusTCPserver_0"/>