KAboutLicense::byKeyword: handle SPDX ids with -or-later
Newer version of SPDX have the variants with + suffix deprecated, in favour of ones with suffix -or-later. See e.g. https://spdx.org/licenses/GPL-3.0+.html vs. https://spdx.org/licenses/GPL-3.0-or-later.html
Follow.-up work might consider updating also KAboutLicense::spdx(), though that first need insight if any code relies on the old ids being returned here.
Would backport to KF5.
Edited by Friedrich W. H. Kossebau