doc/filters: fix grammar for removelogo filter doc sentence
doc/filters: readjust w/h option descriptions
lavfi/transpose: restore validity of values in range 4-7

They were lost in commit a4e0defa75b6f766aa31d80c55688d036b5fd87b.
lavfi/transpose: reindent constants
doc/filters: update/extend transpose filter documentation

In particular, deprecate numerical values for the dir option.
lavu/mem: remove redundant comment from av_dynarray_add()

The function is documented in mem.h.
ffv1enc: favor version 3 over 2 unless -strict -2 is set

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>