[TLBB] Opengl work
Fix XBMC init.d script

Init.d scripts are not intended to run in a never ending loop. Among
other problems it disables the ability to log on the serial console.
Now the XBMC init.d script launches a background subshell and do necessary
things there.

xbmc-pre and xbmc-post scripts were included there too.
Use standard login with getty (generic serial)
openssh: add option to build sftp-server only

Lightweight ssh server implementations (Dropbear) usually lacks sftp
implementation but they can be used with one comming from openssh package.
With this option only sftp-server executable is built and installed into
/usr/libexec.
dropbear: add option to use sftp-server from openssh
PACKAGE: Bump librtmp to 2.4 with ksv patch
[TLBB] Meson3 work again