SPECFEM2D v8.0.0

New in SPECFEM2D 8.0.0:

• GPU support
• axisymmetric 2.5D simulations
• various code improvements

many thanks for all your contributions to this version:
Etienne Bachmann, Alexis Bottero, Bryant Chow, Paul Cristini, Rene Gassmoeller, Michael Gineste, Felix Halpaap, Dimitri Komatitsch, Matthieu Lefebvre, Qiancheng Liu, Qinya Liu, Zhaolun Liu, David Luet, Ryan Modrak, Christina Morency, Daniel Peter, Eric Rosenkrantz, Herurisa Rusmanugroho, Elliott Sales de Andrade, Eduardo Valero Cano, Zhinan Xie, Zhendong Zhang