* switch to fork of the Ada runtime provided by m-stein
* switch to a Ada-runtime state that provides the Exp_Int package (exponential
function on integers)
* adapt spark lib, symbols, and recipes to incorporate the Exp_Int package
Fixes#3848
The minimal-footprint Ada runtime for implementing library-like
functionality in SPARK is now called "spark" runtime.
The full Ada runtime for entire components written in Ada and using the
libc as glue to the underlying system will move to the world repository
as "ada" runtime.
Issue #3144
