autotrace (optionally) pulls both imagemagick6 and pstoedit, while
the latter also pulls imagemagick7. Since imagemagick6 conflicts
with imagemagick7 and autotrace does not support imagemagick7, one
of the options need to be disabled by default to avoid the conflict.
Disabling PSTOEDIT in assumption that raster image support would be
more useful than postscript support.
Approved by: portmgr blanket
10672193d0