This implies creating a trimmed down branch that contains almost
nothing. It will then be usable by projects that do not need the
complex build system, and by the engine itself as a submodule from
the same repository.

This new version allows to compute odd and even double factorials
without harming performance for the standard factorial.

Most operators do not yet handle reals of different sizes, but
this change fixes the most glaring bugs.

It was hard to avoid some of the compiler optimisations caused by our
intermediate conversion to double, so we hide them behind the actual
real object. Also, this commit fixes a potential exponent overflow.

Now that the exponent is no longer biased, it is a signed number, and we
need to account for that when dividing it and expecting rounding rules to
behave in a certain way.

Some checks are failing, I probably messed up several functions.

By adding a bias we ensure that 1.999… will be displayed as 2.0 as long as we
do not ask for too many digits, and that rounding is reasonable for most values.
Note that our need for proper rounding is not as high as for IEEE floats since
we have an insane amount of digits at our disposal.

Also we now get rid of trailing zeroes when printing reals.

The name “re” came from “reciprocal” but since we have “inverse” for
matrices, I thought it would be nice to make everything consistent.

to get M_PI from the platform headers and cast it to float.

computation function.

compilation time for very little benefit and maybe even confusion.

computed on demand with static initialisation.

fully initialised.

"shader" source directory since we have "gpu".