PLCgen: Exceeded maximum number of blocks in PLC-code for CPU

During testing of the code a new error showed up: "Maximum number of 1024 blocks permitted for this CPU was exceeded".

Indeed we see from the generated PLC-code that the number of blocks for events and timers is close to this limit. As we need to add more events this number will only increase, so it doesn't look possible anymore to generate a separate function block for every event.

Any ideas how to change this? This has a high priority for us, as this stops us from continuing our work.

Addresses #679