Adjust implementation of table functions

[4z0t]

• table.getsize used to return 0 when given non table value. Make asm implementation do the same as well. related to Always return a number from table.getn and table.getsize #97;
• implement table.getsize in C++;
• implement table.empty in C++.
• don't use asm to register new functions

[Garanas]

I've done a few AI vs AI games and they appear to run fine. I'll do a few manual tests next.

[4z0t]

Made it compatible with Python patcher