* Allows more interpolation magic.
* Revealed an issue with `interpolatedanglef()` that was undetected. Removed in place of a binangle version returned as floating point build.
* Added in fca846272e to deal with signed adjustments but its just not needed.
* Made better use of `binangle`/`fixedhoriz` class getters and setters than before as well.
* why the reference parameters? These should be passed by value.
* removed the < and > operators from binangle class because angles should not be ordered.
* instead of calling the CRT trig functions, use the ones from cmath.h which are more reliable
* Struct made up of binangle class units.
* Create signed clone of binangle for use with look_ang and rotscrnang.
* Append currently outgoing function names with `2` at the end to avoid conflict.
* Determined maximum horizon able to be handed by engine in Q16.16 format is 280039127.
* Re-did pitch math to work on this known maximum and standardised pitch around -90/90 degrees as it should be.
* Because pitch is now -90/90 and not ~-188/188, m_sensitivity_y probably requires re-scaling.
* Remove fix16.h/cpp and utilise library from m_fixed.h.
* Extend m_fixed.h with two inline functions for int to/from float operations.
* Replace fix16_floor operations with those from xs_Float.h
* Replace multiple Q16.16 conversions from 0 to just be 0.
* Replaced all found in-game bit-shifts and multiplications/divisions with inline functions from m_fixed.h
* Replaced many casts of FRACUNIT as double in SW's panel.cpp as it is converted to double by way of type promotion.
* Fixed missed precision fixes in SW's panel.cpp where some types weren't declared correctly.
* Replaced 100+ `Cos()/Sin() >> 16` operations for Blood with inline functions `CosScale16()/SinScale16()`.
* Can't have a - operator on unsigned int in the binangle class.
* Changed fixed horiz class from unsigned to signed as in-game horizon is a signed integer.
