- Add license headers to source files (years based on commit dates)
in `src/test` as well as `qa`
- Add `README.md` to `src/test/data` specifying MIT license
Fixes#3848
Use misc methods of avoiding unnecesary header includes.
Replace int typedefs with int##_t from stdint.h.
Replace PRI64[xdu] with PRI[xdu]64 from inttypes.h.
Normalize QT_VERSION ifs where possible.
Resolve some indirect dependencies as direct ones.
Remove extern declarations from .cpp files.
