downstem 64th and 128th flag touchup (issue4273074)

[lemniskata . bernoullego]

This changes correspond to
http://lists.gnu.org/archive/html/lilypond-devel/2011-03/msg00399.html

(You can see changes in fonts by running
  mf '\mode:=proof; input feta-noteheads20'
  gftodvi feta-noteheads20.2602gf
from /mf directory and comparing dvi files before and after a patch,
or compiling a simple proof-sheet:
    \paper { ragged-right  = ##t }
    \relative c'' { \autoBeamOff
        e8 e16 e32 e64 e128 f8 f16 f32 f64 f128 \bar "" \break
        f,8 f16 f32 f64 f128 e8 e16 e32 e64 e128
      }
Proof-sheets compiled by me can be downloaded from here:
http://www.sendspace.com/file/oyprjc
http://www.sendspace.com/file/ue5klk
)


http://codereview.appspot.com/4273074/