These warnings were always enabled, but we didn't see them due to https://gitlab.com/OpenMW/openmw/-/issues/7882.
I do not fully understand the cause of 7822 as I can't repro it in a minimal CMake project.
Some of these fixes are thought through.
Some are sensible best guesses.
Some are kind of a stab in the dark as I don't know whether there was a
possible bug the warning was telling me about that I've done nothing to
help by introducing a static_cast.
Nearly all of these warnings were about some kind of narrowing
conversion, so I'm not sure why they weren't firing with GCC and Clang,
which have -Wall -Wextra -pedantic set, which should imply -Wnarrowing,
and they can't have been affected by 7882.
There were also some warnings being triggered from Boost code.
The vast majority of library headers that do questionable things weren't
firing warnings off, but for some reason, /external:I wasn't putting
these Boost headers into external mode.
We need these warnings dealt with one way or another so we can switch
the default Windows CI from MSBuild (which doesn't do ccache) to Ninja
(which does).
I have the necessary magic for that on a branch, but the branch won't
build because of these warnings.
Prevents compiler warnings such as this:
```
/Users/Will/CLionProjects/OpenMW/apps/openmw/mwgui/windowbase.hpp:65:22: warning: 'onOpen' overrides a member function but is not marked 'override' [-Winconsistent-missing-override]
virtual void onOpen();
^
/Users/Will/CLionProjects/OpenMW/apps/openmw/mwgui/windowbase.hpp:38:22: note: overridden virtual function is here
virtual void onOpen() {}
^
```
Remember which button was pressed until a new interactive message box is
displayed or until the pressed button number is read.
Before that, it was not possible to get the pressed button after the
message box was hidden/destroyed.
I made a bunch of changes in apps/openmw/mwrender/animation.cpp
because the scope brackets didn't line up in a bunch of places
npcanimations.cpp & creatureanimations.cpp were the same kind of
thing