Limit source code to 80 chars, and declare functions return type and
modifiers on a separate line.
This allows to avoid very long lines, and all function names are
aligned.
(We do this on VLC, and I like it.)
Mouse events position were unsigned (so negative values could not be
handled properly).
To avoid issues with negative values, mouse events outside the device
screen were ignored (commit a7fe9ad779).
But as a consequence, drag&drop were "broken" if the "drop" occurred
outside the device screen.
Instead, use signed 32-bits to store the position, and forward events
outside the device screen.
Fixes <https://github.com/Genymobile/scrcpy/issues/357>.
