sundials in Octave core

[c.]

Hi,

I just pushed a sequence of changesets that implement ode15i and ode15s
based on sundials:

http://hg.savannah.gnu.org/hgweb/octave/rev/31bd8a50d44c
http://hg.savannah.gnu.org/hgweb/octave/rev/ee1c77705fcd
http://hg.savannah.gnu.org/hgweb/octave/rev/4c56f3ffec04
http://hg.savannah.gnu.org/hgweb/octave/rev/284bbb0328f2
http://hg.savannah.gnu.org/hgweb/octave/rev/51c9eded34ee
http://hg.savannah.gnu.org/hgweb/octave/rev/a1f1ab76aa64

As a side effect, if this feature is enabled, Octave will link by default
with sundials.

IIRC Bill was trying to implement some other missing Matlab functions in Octave
by using sudials but was having problems in linking to both Octave and 
sundials, 
but this should now be straightforward.

c.