Clang-format sees the text behind `#pragma region` as code and formats it. Instead of stating the copyright and date there, it's now in the comment block right below it. The text "Copyright" is left in the `#pragma region` line, as clang-format sees it as a single identifier.
I took the opportunity to normalize the dates, and add the copyright notice to the source files where it was missing them (except for third-party and the generated resources.h file).
This commit expands tabs to spaces (ts=4) in all the files under src/
and test/.
Until now we had two wildly different code styles with C using tabs and
new C++ using spaces. It is painful to maintain as none of the commonly
used tools support this kind of setup and in reality is needless, as we
can simply convert all the sources to spaces and have opened PRs do the
same, where needed.
Additionally, trailing whitespace has been removed.
