Problem:
- `typedef`s are read backwards making it confusing.
- `using` statements can be used in template aliases.
- `using` provides similarity to most other C++ syntax.
- C++ core guidelines say to prefer `using` over `typedef`:
https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rt-using
Solution:
- Switch these where appropriate.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
