Update R-pixmap to 0.4.9

Changes in pixmap version 0.4-9

  o Fixed a minor glitch in write.pnm.

Changes in pixmap version 0.4-8

  o Fixed a bug that prevented plotting images with only 1 row (bug
    report by Robert Esswein).

Changes in pixmap version 0.4-7

  o Use LazyLoad instead of SaveImage.

Changes in pixmap version 0.4-6

  o Modified one of the regression tests for changes in R 2.4:
    terrain.colors() now return transparency information
    -> do not use it in example.

Changes in pixmap version 0.4-5

  o standardized license filed in DESCRIPTION file.

(markd)