Fix: all casting

[Jamesbarford]

• You have to now forward define classes
• Casting works 1:1 with templeOS (need to remove cast<>)
• Added StrTrim<> routines
• Fix: print I8
• Assembly generation will do a cast and then assign to it when doing someting like

I64 i = 0, x=10, z=125;
i(I8) = (x + z)(I64);

// `i` will overflow