Revert "libpng 1.6.10 enable NEON Optimizations"

breaks builds, more investigation needed

This reverts commit 61c00d54ff8b296a449a1810d2acc87262dfc314.

Change-Id: I5b607b8316fb3a61bc67d4077b0b7d5ceb9ea2d6
diff --git a/Android.mk b/Android.mk
index f545581..2551612 100644
--- a/Android.mk
+++ b/Android.mk
@@ -20,7 +20,10 @@
 	pngwtran.c \
 	pngwutil.c \
 
-my_cflags_arm := -DPNG_ARM_NEON_OPT=2 -DPNG_ARM_NEON_CHECK_SUPPORTED
+# Previously these arm-specific flags were never applied.
+# TODO: apply the flags and fix the build.
+# my_cflags_arm := -DPNG_ARM_NEON_OPT=2 -DPNG_ARM_NEON_CHECK_SUPPORTED
+my_cflags_arm :=
 
 # BUG: http://llvm.org/PR19472 - SLP vectorization (on ARM at least) crashes
 # when we can't lower a vectorized bswap.