restructuring: implement all math functions from the Half-Life SDK

[SmileyAG]

It will be comfortable for those who want to port changes to/from BXT without a doing much changes

I think these functions should not be optimized in any way by using simpler solutions or those that consume less performance, because this may still somehow affect the result depending how it implemented in library we using it from, I would prefer to have absolutely the same behavior as in the HLSDK, even if in some cases it may produce the wrong result, but at least it will be the same behaviour as in the original game

But if someone thinks differently, then please share your comment, I will be glad to know your opinion on this matter

[YaLTeR]

I think these functions should not be optimized in any way by using simpler solutions or those that consume less performance, because this may still somehow affect the result depending how it implemented in library we using it from

If you're reimplementing it's already a lost cause. Even if you copy the source it can easily mismatch.