[libng16] Neglected to check in pngconf.h with previous commit.
diff --git a/pngconf.h b/pngconf.h
index 5e087e9..23eee52 100644
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,7 +1,7 @@
/* pngconf.h - machine configurable file for libpng
*
- * libpng version 1.6.3beta07 - May 12, 2013
+ * libpng version 1.6.3beta07 - June 6, 2013
*
* Copyright (c) 1998-2013 Glenn Randers-Pehrson
* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
@@ -194,6 +194,30 @@
* PNG_USE_DLL is set.
*/
+/* Compile time options.
+ * =====================
+ * In a multi-arch build the compiler may compile the code several times for the
+ * same object module, producing different codes for different architectures.
+ * When this happens configure-time setting of the target host options cannot be
+ * done and this interferes with the handling of the ARM NEON optimizations, and
+ * possibly other similiar optimizations. Put additional tests here; in general
+ * this is needed when the same option can be changed at both compile time and
+ * run time depending on the target OS (i.e. iOS vs Android.)
+ */
+#ifdef __ARM_NEON__
+ /* If the default below causes problems set PNG_ARM_NEON_NOT_SUPPORTED either
+ * by passing --enable-arm-neon=no to configure or setting it in some other
+ * way when pnglibconf.h is built.
+ */
+# if (!defined PNG_ARM_NEON_SUPPORTED) && (!defined PNG_ARM_NEON_NOT_SUPPORTED)
+# define PNG_ARM_NEON_SUPPORTED
+# endif
+#endif
+
+#if (defined PNG_ARM_NEON_SUPPORTED) && (defined PNG_ARM_NEON_NOT_SUPPORTED)
+# error configuration: ARM_NEON cannot both be supported and disabled
+#endif
+
/* System specific discovery.
* ==========================
* This code is used at build time to find PNG_IMPEXP, the API settings
