remove deprecated code
revert remove of iterator() and list()
trac #16909: Merged with 6.4.beta3
trac #17023: Poset.width and Poset.dilworth_decomposition
trac #17023: Reviwer's remarks
trac #17023 code and doc formatting + one ref
trac #17095 more doc for plancherel measure
Disallow pari(None), improve docs for Strexpand()
Corrected complements() function of lattices.
Remove extra spaces.
Added check for empty lattice.
Some corrections.
One more change.
Merge remote-tracking branch 'origin/develop' into depr_func
deprecate compact argument
Mark Strexpand() doctests random
Trac #16933: Remove deprecated code

Remove code deprecated in #7983, #13109, #13605, #13192, #14063.

URL: http://trac.sagemath.org/16933
Reported by: aapitzsch
Ticket author(s): André Apitzsch
Reviewer(s): Jeroen Demeyer
Trac #17119: Disallow pari(None)

Currently, `pari(None)` behaves like `pari("None")`, i.e. the monomial
of degree 1 in the variable `None`. Instead, we should raise an
exception for `pari(None)`.

Also clarify the docs of `Strexpand()` (which is how I found out about
this bug).

URL: http://trac.sagemath.org/17119
Reported by: jdemeyer
Ticket author(s): Jeroen Demeyer
Reviewer(s): Peter Bruin
Trac #17138: LatticePoset: complements() is broken

Complement of an element of lattice, if it exists, is not necessarily
unique. Hence returning an array from `complements()` seems to be
totally wrong. Right way is to return a dict of lists if called without
arguments and a list if called with one element as argument.

To clarify what is wrong in all possible meanings for a function called
"complements":

{{{
sage: Posets.PentagonPoset().complements()
[4, 3, 1, 1, 0]
sage: LatticePoset({'a':'b'}).complements()
[1, 0]
}}}

URL: http://trac.sagemath.org/17138
Reported by: jmantysalo
Ticket author(s): Jori Mäntysalo
Reviewer(s): Nathann Cohen
Trac #17023: Adding width() function to poset

Add a `.width()` -- i.e. number of elements in the longest antichain --
to poset. Seems to have polynomial time algorithm based on Dilworth's
Theorem.

URL: http://trac.sagemath.org/17023
Reported by: jmantysalo
Ticket author(s): Nathann Cohen
Reviewer(s): Frédéric Chapoton, Jori Mäntysalo