Use virtual operators in vector.h

[foxtacles]

In reference to: #1193

I've been thinking more about this, and considering that even in the BETA, all the arithmetic operations always and consistently use dynamic dispatch, I figured whatever it is, it must have been present in the BETA as well.

Then I randomly tried making the arithmetic operations virtual operator functions, and it turns out that for some arcane reason, MSVC 4.20 always uses dynamic dispatch for virtual functions that are operators, even if they for all intents and purposes should be inlined. Since operators in C++ are essentially just regular functions (with an extra way of calling them using the operator syntax) I did not expect that the compiler would treat them differently, but here we are.

I think this solves the mystery once and for all. It should also clean up BETA matches since the calls are now correct.