Fix bugs
Silence travis
Don't break gcc
Hopefully don't crash
Add missing PARAM bytecode handler
Less UB
Should really use variant and the new strings, but that's too hard
Addition is NOT symmetrical, internally
Don't crash for another thing that probably shouldn't happen, but does
Count the number of online players again

I refactored two adjacent loops into one, but forgot to merge this!
Hopefully fix the trade heisenbug
Make callfunc/callsub in an if an error

Also make all errors fatal and clean up messages a bit.
Add all conversions, and optimize a temporary case
Poison std::string and use the various string classes