Upgrade readline to version 6.3

Used tarball is ftp://ftp.cwru.edu/pub/bash/readline-6.3.tar.gz
Simplify patches after more thorough investigation
Update to Readline version 6.3.008

Created tarball with
$ git clone git://git.sv.gnu.org/readline.git
$ git archive --format=tar.gz --prefix=readline-6.3.008/ -o readline-6.3.008.tar.gz HEAD
(where HEAD is at a73b98f779b388a5d0624e02e8bb187246e3e396 Readline-6.3
patch 8)
trac #17056: correct __dealloc__ and __getitem__
#17602 doctest output fix
Trac #17056: fix doctest
Trac #17056: Bugs in WordDatatype_char

There are two bugs with WordDatatype_char (new datastructure for words
introduced in #17013):
- in `__dealloc__` we access a Python attribute... it is very bad since
Cython is such that they are deallocated before the call to
`__dealloc__`. In different situations sage terminates because of a
memory corruption
- in `__getitem__` we had
  {{{
  sage: W = Words([0,1,2])
  sage: w = W([0,1,0])
  sage: w[1:0]
  word: ... <RANDOM STUFF> ...
  }}}

URL: http://trac.sagemath.org/17056
Reported by: vdelecroix
Ticket author(s): Vincent Delecroix
Reviewer(s): Sébastien Labbé
Trac #17062: Fix an optional doctest output after #16746

After #16746, output of dicts is sorted by index, and this results in
one test in  src/doc/en/bordeaux_2008/elliptic_curves.rst failing when
the optional database_cremona_ellcurve database is installed:
{{{
sage: C = CremonaDatabase()
sage: C[37]
{'allbsd': {'a1': [1,
   5.98691729246392,
   0.305999773834052,
   0.0511114082399688,
   1.0],
...
}}}
is what comes out, since the field with key 'allbsd' which only exists
in the optional larger database comes before key 'allcurves' which is in
the standard version.  I propose replacing the test with
{{{
sage: C = CremonaDatabase()
sage: C[37]['allcurves']
{'a1': [[0, 0, 1, -1, 0], 1, 1],
 'b1': [[0, 1, 1, -23, -50], 0, 3],
 'b2': [[0, 1, 1, -1873, -31833], 0, 1],
 'b3': [[0, 1, 1, -3, 1], 0, 3]}
}}}
and will make this change soon.

URL: http://trac.sagemath.org/17062
Reported by: cremona
Ticket author(s): John Cremona
Reviewer(s): Volker Braun
Trac #16480: Upgrade readline to version 6.3

This is needed to build on Arch. (Of course the build breaks again when
Arch gets the next readline version and corresponding bash.)

The tarball is at [http://www.ixsop.nl/sage/readline-6.3.008.tar.gz].

URL: http://trac.sagemath.org/16480
Reported by: emassop
Ticket author(s): Erik Massop
Reviewer(s): Volker Braun