As soon as the stream is started, the video buffer could notify a new
frame available.

In order to pass this event to the screen without race condition, the
screen must be initialized before the screen is started.

A skipped frame is detected when the producer offers a frame while the
current pending frame has not been consumed.

However, the producer (in practice the decoder) is not interested in the
fact that a frame has been skipped, only the consumer (the renderer) is.
Therefore, expose the skipped count in consumer_take_frame() instead of
a flag in the producer_offer_frame().

This allows to manage the skipped and rendered frames count at the same
place, and remove fps_counter from decoder.

Make the decoder independant of the SDL even mechanism, by registering a
callback on the video_buffer.

Video buffer is a tool between a frame producer and a frame consumer.

For now, it is used between a decoder and a renderer, but in the future
another instance might be used to swscale decoded frames.

In order to make video buffer more generic, move out its specific
responsibility to count the fps between the decoder and the renderer.

Now that all screen-related events are handled from screen.c, there is
no need for a separate method for window events.

This paves the way to handle EVENT_NEW_FRAME from screen.c, by allowing
to call screen_update_frame() without an explicit video_buffer instance.

After the struct screen is initialized, the window and the renderer are
necessarily valid, so there is no need o check in screen_destroy().

This will avoid corner cases where we need to resize while no frame has
been received yet.

The flag is used only locally, there is no need to store it in the
screen structure.

There were only two frames simultaneously:
 - one used by the decoder;
 - one used by the renderer.

When the decoder finished decoding a frame, it swapped it with the
rendering frame.

Adding a third frame provides several benefits:
 - the decoder do not have to wait for the renderer to release the
   mutex;
 - it simplifies the video_buffer API;
 - it makes the rendering frame valid until the next call to
   video_buffer_take_rendering_frame(), which will be useful for
   swscaling on window resize.

Add a function to assert that the mutex is held (or not).

The goal is to expose a consistent API for system tools, and paves the
way to make the "core" independant of SDL in the future.

The functions SDL_malloc(), SDL_free() and SDL_strdup() were used only
because strdup() was not available everywhere.

Now that it is available, use the native version of these functions.

Make strdup() available on all platforms.

The port_range is used from "struct server_params", the copy in
"struct server" was unused.

Small unsigned integers promote to signed int. As a consequence, if v is
a uint8_t, then (v << 24) yields an int, so the left shift is undefined
if the MSB is 1.

Cast to uint32_t to yield an unsigned value.

Reported by USAN (meson x -Db_sanitize=undefined):

    runtime error: left shift of 255 by 24 places cannot be represented
    in type 'int'

Terminating the file handler current process may be either a "push" or
"install" command.

An "adb push" command is not terminated by SIGTERM.

The current process could be waited both by run_file_handler() and
file_handler_stop().

To avoid the race condition, wait the process without closing, then
close with mutex locked.

There were two versions: process_wait() and process_wait_noclose().

Expose a single version with a flag (it was already implemented that way
internally).

The function process_wait() returned a bool (true if the process
terminated successfully) and provided the exit code via an output
parameter exit_code.

But the returned value was always equivalent to exit_code == 0, so just
return the exit code instead.

The function control_msg_serialize() returns a size_t.

This enables necessary functions once for all.

As a consequence, define common.h before any other header.

Include config.h and compat.h in common.h, and include common.h from all
source files.

The size, point and position structs were defined in common.h. Move them
to coords.h so that common.h could be used for generic code to be
included in all source files.

The header libavformat/version.h was included, but not
libavcodec/version.h.

As a consequence, the LIBAVCODEC_VERSION_INT definition depended on the
caller includes.

It had been replaced by struct sc_port_range in scrcpy.h.

On Linux, waitpid() both waits for the process to terminate and reaps it
(closes its handle). On Windows, these actions are separated into
WaitForSingleObject() and CloseHandle().

Expose these actions separately, so that it is possible to send a signal
to a process while waiting for its termination without race condition.

This allows to wait for server termination normally, but kill the
process without race condition if it is not terminated after some delay.

Adding "simple" in the function name brings no benefit.