fixup: use thread-local buffer
fixup: use thread-local buffer

start with 0 bytes length (saves memory in case lz4 is not used).
always grow when a bigger buffer is needed.
avoid per-call reallocation / freeing / garbage.

raxenak/borg,raxenak/borg,edgimar/borg,edgewood/borg,RonnyPfannschmidt/borg,edgewood/borg,edgewood/borg,raxenak/borg,edgimar/borg,RonnyPfannschmidt/borg,RonnyPfannschmidt/borg,edgimar/borg,raxenak/borg,RonnyPfannschmidt/borg,edgewood/borg,edgimar/borg,RonnyPfannschmidt/borg