RELEASE: update to 2.4.git

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: James Almer <jamrial@gmail.com>
avutil: remove obsolete FF_API_LLS1 cruft

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: James Almer <jamrial@gmail.com>
avutil: remove obsolete FF_API_OLD_OPENCL cruft

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: James Almer <jamrial@gmail.com>
avfilter: remove obsolete FF_API_BUFFERSRC_BUFFER cruft

Reviewed-by: Michael Niedermayer <michaelni@gmx.at>
Signed-off-by: James Almer <jamrial@gmail.com>