The header scrcpy.h is intended to be the "public" API. It should not
depend on other internal headers.
Therefore, declare all required structs in this header and adapt
internal code.
Accept a range of ports to listen to, so that it does not fail if
another instance of scrcpy is currently starting.
The range can be passed via the command line:
scrcpy -p 27183:27186
scrcpy -p 27183 # implicitly 27183:27183, as before
The default is 27183:27199.
Closes#951 <https://github.com/Genymobile/scrcpy/issues/951>