Dynamically load libudev.so.1 on Linux if udev=yes

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
```

misc/scripts/file_format.sh

@@ -30,6 +30,8 @@ while IFS= read -rd '' f; do
         continue
     elif [[ "$f" == "platform/android/java/lib/src/com/google"* ]]; then
         continue
+    elif [[ "$f" == *"-so_wrap."* ]]; then
+        continue
     fi
     # Ensure that files are UTF-8 formatted.
     recode UTF-8 "$f" 2> /dev/null