Fix build with Boost 1.81.0. `<array>` was included by one of those boost headers,
however, it's no longer included as of Boost 1.81.0.
`master` doesn't use `std::array` in this file.
While we're at it, add all necessary inclusion files.
Since we switched from autotools to Meson in commit
94592c1406, we don't need to include
`config.h` early to properly enable large file support. Meson passes
the required macros on the compiler command line instead of defining
them in `config.h`.
This means we can include `config.h` at any time, whenever we want to
check its macros, and there are no ordering constraints.
