Hi,

the following patch allows for use different input image formats by
using convert(1) to generate Face and X-Face headers.
Currently `gnus-x-face-from-file' requires GIF and
`gnus-face-from-file' requires JPEG.

For me, the current `gnus-x-face-from-file' command doesn't even work
(and I saw similar reports on Google):

$ giftopnm face.gif | ppmnorm | pnmscale -width 48 -height 48 | ppmtopgm |\
  pgmtopbm | pbmtoxbm | compface
giftopnm: Reading Image Sequence 0
ppmnorm: remapping 65..233 to 0..255
compface: (warning) <stdin>: excess data ignored
compface: (warning) <stdin>: excess data ignored
$


Is it okay to change the defaults?