Bugs, bugs, bugs... and also a small code clean.

- Fixed `if_` opcodes with arguments: `int, float` and `float, int`
- Fixed typos in TOpParam operators when both types were `float`
- Fixed opcodes add/sub/mul/div when called with first parameter as
char-pointer stackval (`[]`)
- Changed bytecode strings saving
- Improved performance
- Cleaned the `Opcodes.pas`