[libpng15] Ensure that NEON filter stuff is completely disabled when

switched 'off'.  Previously the ARM NEON specific files were still built
if the option was switched 'off' as opposed to being explicitly disabled.

arm/filter_neon.S

@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2013 Glenn Randers-Pehrson
  * Written by Mans Rullgard, 2011.
- * Last changed in libpng 1.5.16 [%RDATE%]
+ * Last changed in libpng 1.5.16 [(PENDING RELEASE)]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -11,7 +11,7 @@
  */
 
 /* This is required to get the symbol renames, which are #defines, and also
- * includes the value of PNG_FILTER_OPTIMIZATIONS.
+ * includes the definition (or not) of PNG_ARM_NEON_SUPPORTED.
  */
 #define PNG_VERSION_INFO_ONLY
 #include "../pngpriv.h"
@@ -20,8 +20,7 @@
 .section .note.GNU-stack,"",%progbits /* mark stack as non-executable */
 #endif
 
-#if defined(PNG_FILTER_OPTIMIZATIONS) && defined(__arm__) && \
-   defined(__ARM_NEON__)
+#ifdef PNG_ARM_NEON_SUPPORTED
 
 #ifdef __ELF__
 #   define ELF
@@ -233,4 +232,4 @@ func    png_read_filter_row_paeth3_neon, export=1
 
         pop             {r4,pc}
 endfunc
-#endif /* FILTER_OPTIMIZATIONS && __arm__ && __ARM_NEON__ */
+#endif /* PNG_ARM_NEON_SUPPORTED */