[BOARD/PACKAGE] add FFMPEG to record&play /dev/fb0 + alsa capture (#48)

* [PACKAGE] downgrade FFMPEG(add) & X264
- use ffmpeg-3.1 thus downgrade ver. to working SDL1.2
- downgrade x264 to be inline with former ffmpeg
- uncomment FFSERVER build instructions (it is available in 3.1 version)

* [BOARD] 
- add `ffplay` & `ffmpeg` apps to record&play
- add `arecord` script for AUDIO capture (use alsaloop workaround)
- update appLinks with "params=&" for bg launch
- use `pkill` instead 'killall` for scripts (warning: it also checks for bash running under the same name)
- use FFPROBE to detect media format in `ffplay`
- for X264  use sources.buildroot.net (code.videolan.org src only works with git method)
- rm redundant usb Applink
- add 0003-ffplay-custom-sdlk.patch (to make hotkeys usable in miyoo)

package/ffmpeg/ffmpeg.hash

@@ -1,5 +1,2 @@
 # Locally calculated
-sha256  6c5b6c195e61534766a0b5fe16acc919170c883362612816d0a1c7f4f947006e  ffmpeg-4.4.3.tar.xz
-sha256  8177f97513213526df2cf6184d8ff986c675afb514d4e68a404010521b880643  COPYING.GPLv2
-sha256  b634ab5640e258563c536e658cad87080553df6f34f62269a21d554844e58bfe  COPYING.LGPLv2.1
-sha256  cb48bf09a11f5fb576cddb0431c8f5ed0a60157a9ec942adffc13907cbe083f2  LICENSE.md
+sha256 919022430e2dad782fabccffdd6c4cae4e7029f84f0701aa662f036a9ca65423 ffmpeg-3.1.tar.xz