reinstate the original, more generic, license for overrides files

...ry/src/com/oracle/truffle/r/library/fastrGrid/fastrGrid.R

...fle.r.library/src/com/oracle/truffle/r/library/stats/lm.R

....r.library/src/com/oracle/truffle/r/library/stats/model.R

...om/oracle/truffle/r/nodes/builtin/base/R/base_overrides.R

...ruffle/r/nodes/builtin/parallel/R/forkcluster_overrides.R

...e/truffle/r/nodes/builtin/parallel/R/mclapply_overrides.R

...om/oracle/truffle/r/nodes/builtin/snow/R/snow_overrides.R

.../oracle/truffle/r/nodes/builtin/tools/R/tools_overrides.R