Revert "- `xs_Float.h`: Add `getint()` getter to `_xs_doubleints` struct."
Revert "- SW: When adjusting horizon in `DoPlayerDeathHoriz()`, just use integer horizon values and not Q16.16."
Revert "- Duke (RR): Clean up some unnecessary `FixedToFloat()` usage with the `fixedhoriz` `asbuildf()` method."
Revert "- `binaryangle.h`: Use `constexpr` on inline functions where it was previously not possible to do so."
Revert "- `m_fixed.h`: Use `constexpr` on inline functions where it was previously not possible to do so."
Revert "- `xs_Float.h`: Convert header to `constexpr`."
This does nor work as it violates the constexpr rules for unions. The code will error out on compilation for accessing an inactive member of a union.
* Removes situations where calling `xs_CRoundToUInt()` and other unsigned inlines would go through extra casts (`uint32_t` > `int32_t` > `uint32_t`).
* Because the native data in the `_xs_doubleints` struct is a union of a double and `uint32_t`, it makes sense to do everything unsigned and convert to `int32_t` if needed instead.
* Allow use of this library in static initialisers.
* Required re-arranging a little bit to order everything so inlines could be used without prototypes.
