Incorporate new functions ichol and ilu into Octave. * NEWS: Announce new functions. * aspell-octave.en.pws: Add new functions names to custom Octave dictionary. * sparse.txi: Add functions to Octave manual. * __unimplemented__.m: Remove functions from unimplemented list. * lu.cc (Flu), luinc.cc (Fluinc), chol.cc (Fchol): Add seealso links in docstrings. * __ichol__.cc: Wrap long lines to less than 80 chars. Remove trailing whitespace. Don't repeat input validation done in ichol.m for internal functions. Avoid resizing retval vector. * __ilu__.cc: Wrap long lines to less than 80 chars. Remove trailing whitespace. Don't repeat input validation done in ichol.m for internal functions. Avoid resizing retval vector. * ichol.m: Rewrite docstring. Use Octave coding conventions (double quotes hash for comments, ! instead of ~). Replace %!error tests not being run with fail(). * ilu.m: Rewrite docstring. Use Octave coding conventions (double quotes hash for comments, ! instead of ~). Replace %!error tests not being run with fail().