libpng: Fix xz dep and build, update to 1.6.23, add license

Version 1.6.17 is too old for Qt5.

libpng/build.sh

@@ -1,9 +1,13 @@
 #!/bin/bash
 
-if [ `uname` == Linux ]; then
-    export CFLAGS="-I$PREFIX/include -L$PREFIX/lib"
-fi
+export CFLAGS="$CFLAGS -I$PREFIX/include -L$PREFIX/lib"
+export CPPFLAGS="$CPPFLAGS -I$PREFIX/include"
+
+./configure --prefix=$PREFIX \
+            --with-zlib-prefix=$PREFIX
 
-./configure --prefix=$PREFIX
 make
+make check
 make install
+
+cp $RECIPE_DIR/libpng-LICENSE.txt $SRC_DIR/libpng-LICENSE.txt

libpng/libpng-LICENSE.txt

@@ -0,0 +1,112 @@
+
+This copy of the libpng notices is provided for your convenience.  In case of
+any discrepancy between this copy and the notices in the file png.h that is
+included in the libpng distribution, the latter shall prevail.
+
+COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
+
+If you modify libpng you may insert additional notices immediately following
+this sentence.
+
+This code is released under the libpng license.
+
+libpng versions 1.0.7, July 1, 2000, through 1.6.21, January 15, 2016, are
+Copyright (c) 2000-2002, 2004, 2006-2016 Glenn Randers-Pehrson, are
+derived from libpng-1.0.6, and are distributed according to the same
+disclaimer and license as libpng-1.0.6 with the following individuals
+added to the list of Contributing Authors:
+
+   Simon-Pierre Cadieux
+   Eric S. Raymond
+   Mans Rullgard
+   Cosmin Truta
+   Gilles Vollant
+   James Yu
+
+and with the following additions to the disclaimer:
+
+   There is no warranty against interference with your enjoyment of the
+   library or against infringement.  There is no warranty that our
+   efforts or the library will fulfill any of your particular purposes
+   or needs.  This library is provided with all faults, and the entire
+   risk of satisfactory quality, performance, accuracy, and effort is with
+   the user.
+
+libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
+Copyright (c) 1998-2000 Glenn Randers-Pehrson, are derived from
+libpng-0.96, and are distributed according to the same disclaimer and
+license as libpng-0.96, with the following individuals added to the list
+of Contributing Authors:
+
+   Tom Lane
+   Glenn Randers-Pehrson
+   Willem van Schaik
+
+libpng versions 0.89, June 1996, through 0.96, May 1997, are
+Copyright (c) 1996-1997 Andreas Dilger, are derived from libpng-0.88,
+and are distributed according to the same disclaimer and license as
+libpng-0.88, with the following individuals added to the list of
+Contributing Authors:
+
+   John Bowler
+   Kevin Bracey
+   Sam Bushell
+   Magnus Holmgren
+   Greg Roelofs
+   Tom Tanner
+
+libpng versions 0.5, May 1995, through 0.88, January 1996, are
+Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
+
+For the purposes of this copyright and license, "Contributing Authors"
+is defined as the following set of individuals:
+
+   Andreas Dilger
+   Dave Martindale
+   Guy Eric Schalnat
+   Paul Schmidt
+   Tim Wegner
+
+The PNG Reference Library is supplied "AS IS".  The Contributing Authors
+and Group 42, Inc. disclaim all warranties, expressed or implied,
+including, without limitation, the warranties of merchantability and of
+fitness for any purpose.  The Contributing Authors and Group 42, Inc.
+assume no liability for direct, indirect, incidental, special, exemplary,
+or consequential damages, which may result from the use of the PNG
+Reference Library, even if advised of the possibility of such damage.
+
+Permission is hereby granted to use, copy, modify, and distribute this
+source code, or portions hereof, for any purpose, without fee, subject
+to the following restrictions:
+
+  1. The origin of this source code must not be misrepresented.
+
+  2. Altered versions must be plainly marked as such and must not
+     be misrepresented as being the original source.
+
+  3. This Copyright notice may not be removed or altered from any
+     source or altered source distribution.
+
+The Contributing Authors and Group 42, Inc. specifically permit, without
+fee, and encourage the use of this source code as a component to
+supporting the PNG file format in commercial products.  If you use this
+source code in a product, acknowledgment is not required but would be
+appreciated.
+
+END OF COPYRIGHT NOTICE, DISCLAIMER, and LICENSE.
+
+A "png_get_copyright" function is available, for convenient use in "about"
+boxes and the like:
+
+   printf("%s", png_get_copyright(NULL));
+
+Also, the PNG logo (in PNG format, of course) is supplied in the
+files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
+
+Libpng is OSI Certified Open Source Software.  OSI Certified Open Source is
+a certification mark of the Open Source Initiative. OSI has not addressed
+the additional disclaimers inserted at version 1.0.7.
+
+Glenn Randers-Pehrson
+glennrp at users.sourceforge.net
+January 15, 2016

libpng/meta.yaml

@@ -1,16 +1,19 @@
 package:
   name: libpng
-  version: 1.6.17
+  version: 1.6.23
 
 source:
-  fn: libpng-1.6.17.tar.gz
-  url: ftp://ftp.simplesystems.org/pub/libpng/png/src/libpng16/libpng-1.6.17.tar.gz
-  md5: 134282f1752dcf4cd81a37b8ff421cef
+  fn: libpng-1.6.23.tar.gz
+  url: ftp://ftp.simplesystems.org/pub/libpng/png/src/libpng16/libpng-1.6.23.tar.gz
+  sha1: 26c68ff9905dbeb85d1cc9c673726e9e0669e7a0
 
 requirements:
   build:
     - zlib
 
+  run:
+    - zlib
+
 about:
   home: http://www.libpng.org/pub/png/libpng.html
   license: Open Source (http://www.libpng.org/pub/png/src/libpng-LICENSE.txt)