[SPI-1945] Add madgraph5amc 3.1.1 and new patch for madgraph5amc 3.1.1 following discussion with Olivier M.
Add madgraph5amc 3.1.1 and new patch for madgraph5amc 3.1.1 following discussion with Olivier M. https://answers.launchpad.net/mg5amcnlo/+question/698236 Mention SPI-1945