Yellow squiggly lines begone!
Done automatically on .cpp files through `run-clang-tidy`, with manual corrections to the mistakes.
If an import is directly used, but is technically unnecessary since it's recursively imported by something else, it is *not* removed.
The tool doesn't touch .h files, so I did some of them by hand while fixing errors due to old recursive imports.
Not everything is removed, but the cleanup should be substantial enough.
Because this done on Linux, code that isn't used on it is mostly untouched.
(Hopefully no open PR is depending on these imports...)

Mostly involves moving contents of OGLRender
to OGLGfx and OGLConfig

SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.

The class NonCopyable is, like the name says, supposed to disallow
copying. But should it allow moving?

For a long time, NonCopyable used to not allow moving. (It declared
a deleted copy constructor and assigment operator without declaring
a move constructor and assignment operator, making the compiler
implicitly delete the move constructor and assignment operator.)
That's fine if the classes that inherit from NonCopyable don't need
to be movable or if writing the move constructor and assignment
operator by hand is fine, but that's not the case for all classes,
as I discovered when I was working on the DirectoryBlob PR.

Because of that, I decided to make NonCopyable movable in c7602cc,
allowing me to use NonCopyable in DirectoryBlob.h. That was however
an unfortunate decision, because some of the classes that inherit
from NonCopyable have incorrect behavior when moved by default-
generated move constructors and assignment operators, and do not
explicitly delete the move constructors and assignment operators,
relying on NonCopyable being non-movable.

So what can we do about this? There are four solutions that I can
think of:

1. Make NonCopyable non-movable and tell DirectoryBlob to suck it.

2. Keep allowing moving NonCopyable, and expect that classes that
   don't support moving will delete the move constructor and
   assignment operator manually. Not only is this inconsistent
   (having classes disallow copying one way and disallow moving
   another way), but deleting the move constructor and assignment
   operator manually is too easy to forget compared to how tricky
   the resulting problems are.

3. Have one "MovableNonCopyable" and one "NonMovableNonCopyable".
   It works, but it feels rather silly...

4. Don't have a NonCopyable class at all. Considering that deleting
   the copy constructor and assignment operator only takes two lines
   of code, I don't see much of a reason to keep NonCopyable. I
   suppose that there was more of a point in having NonCopyable back
   in the pre-C++11 days, when it wasn't possible to use "= delete".

I decided to go with the fourth one (like the commit title says).
The implementation of the commit is fairly straight-forward, though
I would like to point out that I skipped adding "= delete" lines
for classes whose only reason for being uncopyable is that they
contain uncopyable classes like File::IOFile and std::unique_ptr,
because the compiler makes such classes uncopyable automatically.

BreakBeforeBraces: Allman apparently includes all styles,
except for AfterUnion (which is false) when using clang-format -dump-config