Implement the UNSIGNED extension type and operations under control of a
language feature flag (-funsigned).
This is nearly identical to the UNSIGNED feature that has been available
in Sun Fortran for years, and now implemented in GNU Fortran for
gfortran 15, and proposed for ISO standardization in J3/24-116.txt.
See the new documentation for details; but in short, this is C's
unsigned type, with guaranteed modular arithmetic for +, -, and *, and
the related transformational intrinsic functions SUM & al.
Moves definitions of the kind arrays into a Fortran MODULE to not only
emit the MOD file, but also compile that MODULE file into an object
file. This file is then linked into libFortranRuntime.so.
Eventually this workaround PR shoud be redone and a proper runtime build
should be setup that will then also compile Fortran MODULE files.
Fixes#89403
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Co-authored-by: Valentin Clement (バレンタイン クレメン) <clementval@gmail.com>
Co-authored-by: Michael Kruse <github@meinersbur.de>
