Update Singular to version 3-1-6.
Update Singular function interface to API changes in Singular 3.1.6.

iiMake_proc function in libsingular no longer returns an sleftv. Instead, the
return value is a boolean error condition and the return value is stored in a
global variable iiRETURNEXPR.
Remove description of deleted patches.
trac #14060: improvement to minimal_quadratic_twist
Trac #10108: more robust interface to mwrank
Trac 10108: Change and shorten one doctest
#8348: Document that find_root only works in fixed (double) precision
Errors in docbuilding should raise an error.
When parallel docbuilding, terminate all workers if an error occurs.
Fix whitespace errors.
Trac #15727: Check for doc build errors in "make doc"

Errors in the documentation should cause the `doc` makefile targets to
fail, but they do not.

URL: http://trac.sagemath.org/15727
Reported by: vbraun
Ticket author(s): John Palmieri
Reviewer(s): Volker Braun
Trac #8348: Document that find_root only works in fixed (double) precision

How can one approximate the root of an equation in arbitrary
precision? For example I want the root of log(x+2) = x to
50 digits of precision:
{{{
sage: (log(x+2)-x).find_root(1,2)
1.1461932206205643
sage: (log(x+2)-x).find_root(1,2,prec=150)
------------------------------------------------------------------------
---
TypeError                                 Traceback (most recent call
last)

/users/caramel/zimmerma/try/<ipython console> in <module>()

/usr/local/sage-core2/local/lib/python2.6/site-
packages/sage/symbolic/expression.so in
sage.symbolic.expression.Expression.find_root
(sage/symbolic/expression.cpp:24383)()

TypeError: find_root() got an unexpected keyword argument 'prec'
}}}

URL: http://trac.sagemath.org/8348
Reported by: zimmerma
Ticket author(s): Paul Zimmermann
Reviewer(s): Marc Mezzarobba
Trac #14060: Improve minimal_quadratic_twist()

We need a better implementation of minimal_quadratic_twist(), for
example if the conductor is square-free then there is no need to do so
much work as is currently done.  Additionally, when j(E)=0 or 1728 the
curve returned is a minimal quadratic twist, but not necessarily the
minimal twist, and it would be a good thing for the documentation to
make this clear.

URL: http://trac.sagemath.org/14060
Reported by: cremona
Ticket author(s): John Cremona
Reviewer(s): Chris Wuthrich
Trac #10108: Calling mwrank(-10) hangs Sage, but uses very little CPU time

Following some very quick hacks at using "fuzz testing" techniques, I
found that

{{{
sage: mwrank(-10)
}}}

just hangs, but does not appear to be using any CPU time. Although I
don't know what this is supposed to do, from discussions on sage-devel,
I understand my suspicions this behavior is an error were correct.

Can someone please select the component appropriately, as I don't have a
clue myself.

URL: http://trac.sagemath.org/10108
Reported by: drkirkby
Ticket author(s): John Cremona
Reviewer(s): Mike Hansen, Chris Wuthrich
Trac #14333: singular-3-1-6 is out

[http://www.singular.uni-kl.de/index.php/news/release-of-
singular-3-1-6.html]

----

Sage should probably upgrade to this version; it won't be painless
though, since my experiments show that what in the changelog is lightly
documented as "interface to iiMake_proc changed" (in the "Internal
changes" section) -- impacts sage.
The API for `iiMake_proc` changed from
{{{
sleftv * iiMake_proc(idhdl pn, package pack, sleftv* sl);
}}}
to
{{{
BOOLEAN iiMake_proc(idhdl pn, package pack, sleftv* sl);
}}}

----

Probably also take care of #12442.

Use git branch.

Upstream tarball at: [http://sage.math.washington.edu/home/jpflori/upstr
eam/singular-3.1.6.tar.bz2]

URL: http://trac.sagemath.org/14333
Reported by: Snark
Ticket author(s): Burcin Erocal
Reviewer(s): Jean-Pierre Flori