Overhaul image, imagesc to use newplot and support low-level invocation form. * scripts/image/image.m: New variable do_new indicates high-level calling form. For high-level invocation, call newplot before __img__. Correct linearity check if vectors are reversed (high-to-low values). Only apply image properties to axes if doing a high-level invocation. * scripts/image/imagesc.m: New variable do_new indicates high-level calling form. Delete subfunction __imagesc__ and incorporate minimal amount of code into imagesc. Only apply climits for high-level invocation.

Things to do before making a release:

  * Update the version number and release date in configure.ac.

  * Update the NEWS file.

  * Update the NEWS-<VERSION>.html, index.in, news.in, and download.in
    files for the web site.

  * Copy tarballs to ftp.gnu.org.

  * Post a release announcement to the help@octave.org and
    info-gnu@gnu.org lists.