DO NOT MERGE Update libpng to 1.6.20

BUG:23265085
Change-Id: I85199805636d771f3597b691b63bc0bf46084833
(cherry picked from commit bbe98b40cda082024b669fa508931042eed18f82)
diff --git a/arm/arm_init.c b/arm/arm_init.c
index 952b802..fb3d50d 100644
--- a/arm/arm_init.c
+++ b/arm/arm_init.c
@@ -3,7 +3,7 @@
  *
  * Copyright (c) 2014 Glenn Randers-Pehrson
  * Written by Mans Rullgard, 2011.
- * Last changed in libpng 1.6.10 [March 6, 2014]
+ * Last changed in libpng 1.6.16 [December 22, 2014]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -17,12 +17,13 @@
 #include "../pngpriv.h"
 
 #ifdef PNG_READ_SUPPORTED
+
 #if PNG_ARM_NEON_OPT > 0
 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED /* Do run-time checks */
 /* WARNING: it is strongly recommended that you do not build libpng with
  * run-time checks for CPU features if at all possible.  In the case of the ARM
  * NEON instructions there is no processor-specific way of detecting the
- * presense of the required support, therefore run-time detectioon is extremely
+ * presence of the required support, therefore run-time detection is extremely
  * OS specific.
  *
  * You may set the macro PNG_ARM_NEON_FILE to the file name of file containing
@@ -130,4 +131,4 @@
    }
 }
 #endif /* PNG_ARM_NEON_OPT > 0 */
-#endif /* PNG_READ_SUPPORTED */
+#endif /* READ */