Implemented fast eval functionality for affine morphisms.

Added the _fastpolys and _fast_eval functions defined for projective morphisms to the functionality for
affine morphisms. New imports were necessary for the functions and the doc examples were changed for affine space.
Added _call_ function to affine_morphism
Trac #17058: adding abelian_vectors, abelian_complexity and alphabet methods to FiniteWord class
Merge with 6.4.beta4

* t/17058_6.4.beta3:
  Trac #17058: adding abelian_vectors, abelian_complexity and alphabet methods to FiniteWord class
Trac #17058: Fixes according to reviewer comments
Trac #17058: Fixes according to reviewer comments #2
trac #17058: small speed up + documentation
trac #17058: optimization in .letters()
Trac #17058: remove the cimport of memset
Merge attempt to merge ticket branch with beta
Merged files that seemed to be causing merge conflict locally

Conflicts:
	src/sage/schemes/affine/affine_morphism.py
Minor fix in affine_morphism
Removed whitespace created during merge
Trac #17058: Merge with #17021 and resolve conflicts
Add missing dependencies of Python packages
Bypass Linux Yama restrictions for ptrace()
Trac #17058: Add abelian_vectors and abelian_complexity method to finite words

Add abelian_vectors and abelian_complexity method to finite words

Following the comment made by Jacques Sakarovitch during Journées
montoises 2014 in Nancy, we deprecate the `parikh_vector` method:

{{{
parikh_vector = deprecated_function_alias(17058, abelian_vector)
}}}

Moreover, we deprecate the argument `alphabet` for the method
`abelian_vector` method because it was a bad design choice to allow to
specify the alphabet in such a method. User should specify the alphabet
in the parent.

URL: http://trac.sagemath.org/17058
Reported by: slabbe
Ticket author(s): Sébastien Labbé
Reviewer(s): Vincent Delecroix
Trac #17089: Bypass Linux Yama restrictions

Certain Linux kernels have a security feature which prevents debugging:
[https://www.kernel.org/doc/Documentation/security/Yama.txt]
This breaks the `sage-CSI` script.

With the `prctl` system call, debugging can be allowed again.

URL: http://trac.sagemath.org/17089
Reported by: jdemeyer
Ticket author(s): Jeroen Demeyer
Reviewer(s): Volker Braun
Trac #17085: Add missing dependencies of Python packages

URL: http://trac.sagemath.org/17085
Reported by: jdemeyer
Ticket author(s): Jeroen Demeyer
Reviewer(s): John Palmieri
Trac #17001: Functionality for fast evaluation of affine morphisms

Implement existing functionality for fast evaluation of projective
morphisms for affine morphisms.

URL: http://trac.sagemath.org/17001
Reported by: gjorgenson
Ticket author(s): Grayson Jorgenson
Reviewer(s): Ben Hutz