This prevents errors when encountering options which have been defined in newer
versions of clang-format, and are invalid in the YAML for the old version.
Bump minimum supported clang-format version to 12 (where `--Wno-error=unknown`
was added).
Use clang-format 12 on CI (13 is not available yet on the Ubuntu 20.04 images).
Disable minimum amount of spaces in comment prefix for now, as it otherwise
modifies the whole codebase. That's something we probably want to use as it
matches our convention, but we should look into fully converting these
comments to our style guide at the same time.
This makes it possibly to run Linux binaries compiled with udev support on
Linux systems which do not provide udev (typically systemd-less distros).
If udev is missing, we fall back to parsing `/dev/input` like when compiled
without udev support (`udev=no`).
Also adding some verbose debug statements to know which method we're using
when debugging Linux joypad issues.
The libudev so wrappers were generated on Mageia 8 with libudev 246.9 using
https://github.com/hpvb/dynload-wrapper:
```
./generate-wrapper.py --include /usr/include/libudev.h --sys-include '<libudev.h>' \
--soname libudev.so.1 --init-name libudev --omit-prefix gnu_ \
--output-header libudev-so_wrap.h --output-implementation libudev-so_wrap.c
```
The application module `app` serves double duties of providing the prebuilt Godot binaries ('android_debug.apk', 'android_release.apk') and the Godot custom build template ('android_source.zip').
As of clang-format 6.0.1, putting the `/* clang-format off */` hint
around our "invalid" `[vertex]` and `[shader]` statements isn't enough
to prevent a bogus indent of the next comments and first valid statement,
so we need to enclose that first valid statement in the unformatted chunk.
