log: improve statistics display

represent 4x4 statistics for I frame, combine I frame log in single line,
preserve space in log
encoder: compilers can't agree on how to print long longs
dct: remove unused static array
log: do not output statistics for disabled features
log: shorten Planar to P
encoder: do not warn of b-pyramid and small bframe value

Many default presets can do this, it is harmless