Implemented LOP4 and VLOP3 from JVET_AJ0054.
This implements JVET-AJ0054, which updated LOP3 -> LOP4 and VLOP2 -> VLOP4 using early cropping.
The software uses a version of SADL with commit 0854e53 that allows for padding=(0,0). However, this commit contains an unused variable which means it is not possible to compile on linux (warnings become errors). Hence, after doing git submodule update to check out sadl, apply the patch fixsadl.patch by doing
cd sadl git apply ../fixsadl.patch