Since "adb forward" fallback has been implemented, it is easy to support
API 19.

Replace the incompatible calls related to MediaCodec to use
minSdkVersion 19 instead of 21.

Add -t/--show-touches option to show physical touches while scrcpy is
running.

See <https://github.com/Genymobile/scrcpy/issues/96>.

And remove gcc from the packages list, clang is available by default.

Fix Typo

Since _scrcpy_ also supports `adb forward`, remove the part about `adb
reverse`.

Make explicit that _adb_ is included in the prebuilt application for
Windows (many users manually download the platform-tools for no reason).

Ctrl+s was mapped to MENU, while Ctrl+m was mapped to APP_SWITCH.

To avoid confusion, swap the shortcuts:
 - Ctrl+m like _M_enu
 - Ctrl+s like _S_witch

This is not obvious to everyone, especially non-developers.

Resize the window to fit the device screen on click on black borders
(same as Ctrl+x).
Suggested-by: NGuillaume Roche <groche@genymobile.com>

Now that instructions are given for both Debian/Ubuntu and Fedora, use
subsections.

Document server and client dependencies separately, to avoid unneeded
packages installation when building using the prebuilt server.

Also remove "zip", since it's only used for building a portable version
(which is not documented in README).

And fix spaces (do not randomly use non-breaking spaces for
indentation).

Middle-click is useless in practice. Use it for HOME.

Right-click was used to turn the screen on. It did nothing when the
screen was already on.

Instead, in that case, press BACK (like Vysor).

Suggested by: <https://www.reddit.com/r/Android/comments/834zmr/introducing_scrcpy_an_app_to_display_and_control/dvfueft/>

Indicate how to run the app from the build directory in README. It's
convenient during development.

And update README.

Paste computer clipboard to the device on Ctrl+v.

The other direction (pasting the device clipboard to the computer) is
not implemented. It would require a communication channel from the
device to the computer, other than the socket used by the video stream.

Set the default video bitrate to 8Mbps. This greatly increase quality on
fast motion, without negative side effects.

Explain how to build, install and run the application.

We encounter some problems with SDL2_image on MSYS2 (Windows), so
implement our own XPM parsing which does not depend on SDL_image.

The input XPM is considered safe (it's in our source repo), so do not
check XPM format errors. This implies that read_xpm() is not safe to
call on any unsafe input.

Although less straightforward, use SDL_CreateRGBSurfaceFrom() instead of
SDL_CreateRGBSurfaceWithFormatFrom() because it is available with SDL
versions older than 2.0.5.

Add a bugdroid icon loaded from an XPM.

To run the app during development, add a recipe "run" to the Makefile.