Update FLINT to version 2.4.
Fix NTL interface tests. Reported by Francois Bissey.
Actually add NTL patch.
Update FLINT to version 2.4.1.
Update flint tarball checksums for recompressed 2.4.1.
Fix test for empty string in FLINT build system.
Trac #15574: Update FLINT to 2.4.1

FLINT 2.4.1 has been released:
* http://www.flintlib.org/news.html

The update should be quite trivial.

Use git branch and vanilla upstream tarball at:
* http://boxen.math.washington.edu/home/jpflori/upstream/flint-2.4.1.tar
.gz
(or at http://flintlib.org)

URL: http://trac.sagemath.org/15574
Reported by: jpflori
Ticket author(s): Jean-Pierre Flori
Reviewer(s): François Bissey, Luca De Feo
Update README.txt re installation with OS X Mavericks
Trac #15783: Update README.txt for OS X Mavericks

Followup to #15319.

URL: http://trac.sagemath.org/15783
Reported by: jhpalmieri
Ticket author(s): John Palmieri
Reviewer(s): Michael Welsh