This crate provides the type alias c_longdouble for FFI interoperability with
C's long double. It does not provide any new types.
The exact type that c_longdouble aliases to is based on
https://hackmd.io/@8W5l8q6-Qyyn_vKh2-L0RQ/rJpZsmcdh. Currently the only
bindings available are for targets where long double is f64. Once the
f128 and f116 RFC becomes
usable, platforms that use f128 will be supported. If the additional float
types RFC lands, bindings for f80
will also be supported.