* Incorporate as a patch upstream commit 0c20dbf059 (diff-acb9169b4ccbac494ced5140d285a015) resolving problems with `-Wno-...` options not being understood by GCC.
* Incorporate as a patch upstream PR https://github.com/ericniebler/range-v3/pull/1202 fixing upstream issue https://github.com/ericniebler/range-v3/issues/1196.
* Compile tests only if we actually want to run them.
* Optionally compile documentation with a `+doc` variant.
* Add `+examples` and `+perf` variants to avoid unnecessary compilation of components usually not required for install.
* Add conditional build-only dependency on Boost when appropriate.
* Install docs, examples and performance tests if built (not part of upstream build instructions).
* Add @chissg as a maintainer.
* record conflicts with compiler versions which don't provide
required c++ standard support
* add doxygen (build) dependency
* add note that range-v3 is header-only as of 0.3.6 and update
package description
- remove the old LGPL license headers from all files in Spack
- add SPDX headers to all files
- core and most packages are (Apache-2.0 OR MIT)
- a very small number of remaining packages are LGPL-2.1-only
