The socket used the device-to-computer direction to stream the video and
the computer-to-device direction to send control events.

Some features, like copy-paste from device to computer, require to send
non-video data from the device to the computer.

To make them possible, use two sockets:
 - one for streaming the video from the device to the client;
 - one for control/events in both directions.

A string is serialized as a length (2 bytes) followed by the string data
(non nul-terminated).

For now, it is used only once, but we will need to serialize strings in
other events.

This will avoid to produce invalid UTF-8 results (although unlikely).

This will help to avoid truncating a UTF-8 string in the middle of a
code point, producing an invalid UTF-8 result.

Add missing tests for serialization and deserialization of control
events.

The framework class android.graphics.Point cannot be used in unit tests.
Implement our own Point.

Several commands were grouped under the same event type "command", with
a separate field to indicate the actual command.

Move these commands at the same level as other control events. It will
allow to implement commands with arguments.

If the stream is stopped, av_read_frame() will be woken up and yield a
corrupted packet. Do not try to decode or record it.

The sockets may be closed and shutdown on server_stop(). This will
interrupt the stream and controller threads more quickly and gracefully.

The cleanup is not linear: for example, the server must be stopped and
its sockets must be shutdown after the stream and controller are stopped
(so that they don't continue processing garbage), but before they are
joined, to avoid a deadlock if they are blocked on a socket read.

Simplify the spaghetti-cleanup by keeping trace of initialization at
runtime.

Partial read is impossible for 1 byte, so net_recv_all() is useless.

Only use 2 branches, using either forward or remote tunnel.

The resulting socket is accessible from the server instance, there is no
need to return it.

This paves the way to use several sockets in parallel.

Replace the file_handler_request_queue implementation by cbuf.

Replace the control_event_queue implementation by cbuf.

Add a circular buffer implementation, to factorize multiple specific
queues implementation.

Add a function to read 16 bits in big-endian to a uint16_t.

So that they can be used both on const and non-const input buffers.

control_event_serialize() returns the number of bytes written, so the
type should be size_t.

The variable condition was not destroyed on strdup() failure.

This will avoid conflicts with future device events.

Use parentheses to avoid unexpected results.

For example, make:

    2 * SERIALIZED_EVENT_MAX_SIZE

expand to:

    2 * (3 + TEXT_MAX_LENGTH)

instead of:

    2 * 3 + TEXT_MAX_LENGTH

The struct control_event does not use mutexes, and net.h does not need
SDL_platform.h.

Previous refactorings broke indentation.

Commit dfed1b25 replaced SDL types by
standard types in sources, but tests were not updated.

To avoid mixing SDL_malloc()/SDL_strdup() with free(), or malloc() with
SDL_free(), always use the SDL version.

Checkstyle wants a specific order of imports.

On pressing Home key on the computer, move the cursor to the beginning
of the line instead of going back to the home screen.

<https://developer.android.com/reference/android/view/KeyEvent.html#KEYCODE_HOME>
<https://developer.android.com/reference/android/view/KeyEvent.html#KEYCODE_MOVE_HOME>

Fixes (part of) <https://github.com/Genymobile/scrcpy/issues/555>.

The file handler owns the filename string, so it needs to free it.
Therefore, it should not be a pointer-to-const.

The file handler owns the serial, so it needs to free it. Therefore, it
should not be a pointer-to-const.

If loading the icon from xpm fails, launch scrcpy without window icon.

<https://github.com/Genymobile/scrcpy/issues/539>

SDL_CreateRGBSurfaceFrom() may return NULL, causing a segfault.

<https://github.com/Genymobile/scrcpy/issues/539>

Some characters may not be injected (e.g. '\r`). Log them instead of
ignoring them silently.