There was already utf8_to_wide_char(), used to correctly execute
commands on Windows.
Add the reverse converter: utf8_from_wide_char(). We will need it to
build the scrcpy-server path based on the executable directory.
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.)
Windows does not support UTF-8, so pushing a file with non-ASCII
characters failed.
Convert the UTF-8 command line to a wide characters string and call
CreateProcessW().
Fixes <https://github.com/Genymobile/scrcpy/issues/422>
