Update to libpng-1.6.40.

ports/libpng/libpng.patch

@@ -1,22 +1,7 @@
-diff -Paur --no-dereference -- libpng.upstream/contrib/libtests/pngvalid.c libpng/contrib/libtests/pngvalid.c
---- libpng.upstream/contrib/libtests/pngvalid.c
-+++ libpng/contrib/libtests/pngvalid.c
-@@ -18,10 +18,7 @@
-  *   transformations performed by libpng.
-  */
- 
--#define _POSIX_SOURCE 1
--#define _ISOC99_SOURCE 1 /* For floating point */
--#define _GNU_SOURCE 1 /* For the floating point exception extension */
--#define _BSD_SOURCE 1 /* For the floating point exception extension */
-+/* PATCH: Get feenableexcept without any feature macros. */
- 
- #include <signal.h>
- #include <stdio.h>
 diff -Paur --no-dereference -- libpng.upstream/contrib/libtests/timepng.c libpng/contrib/libtests/timepng.c
 --- libpng.upstream/contrib/libtests/timepng.c
 +++ libpng/contrib/libtests/timepng.c
-@@ -22,6 +22,10 @@
+@@ -21,6 +21,10 @@
  #include <errno.h>
  #include <limits.h>
  
@@ -30,7 +15,7 @@ diff -Paur --no-dereference -- libpng.upstream/contrib/libtests/timepng.c libpng
 diff -Paur --no-dereference -- libpng.upstream/contrib/tools/pngcp.c libpng/contrib/tools/pngcp.c
 --- libpng.upstream/contrib/tools/pngcp.c
 +++ libpng/contrib/tools/pngcp.c
-@@ -70,6 +70,10 @@
+@@ -73,6 +73,10 @@
  #include <limits.h>
  #include <assert.h>
  

ports/libpng/libpng.port

@@ -1,10 +1,10 @@
 NAME=libpng
 BUILD_LIBRARIES=libz
-VERSION=1.6.37
+VERSION=1.6.40
 DISTNAME=$NAME-$VERSION
 COMPRESSION=tar.xz
 ARCHIVE=$DISTNAME.$COMPRESSION
-SHA256SUM=505e70834d35383537b6491e7ae8641f1a4bed1876dbfe361201fc80868d88ca
+SHA256SUM=535b479b2467ff231a3ec6d92a525906fb8ef27978be4f66dbe05d3f3a01b3a1
 UPSTREAM_SITE=https://download.sourceforge.net/libpng
 UPSTREAM_ARCHIVE=$ARCHIVE
 LICENSE=Libpng