Update to 1.6.34

Test: Covered by existing tests.

This is the same version we will use in Chromium:
https://chromium-review.googlesource.com/c/chromium/src/+/704209

https://github.com/glennrp/libpng/commit/edef058e180be435afd8feebb742a22360a7fa3f
(included in this revision) moved the SSE opts directly into the main
libpng source, so contrib/intel/intel_sse.patch is no longer necessary,
as its changes are already included.

Adds *all* code, rather than selecting just the code we use.

Other changes:
- README.android:
  - Update version
  - Android.mk -> Android.bp
  - Remove no longer relevant comment about applying the intel patch
  - Remove comment about deleting unused files
- README.version:
  - Update version and source link

Change-Id: Ib24cfcfec3e2f63eed8b3b9f0920b1018b30dd64
diff --git a/README.android b/README.android
index f6062c6..80e837e 100644
--- a/README.android
+++ b/README.android
@@ -1,9 +1,9 @@
-Any Android specific modifications to upstream libpng (1.6.25) should
+Any Android specific modifications to upstream libpng (1.6.34) should
 be listed here:
 
 (1) Android has added the following files.
     pngusr.h
-    Android.mk
+    Android.bp
     CleanSpec.mk
     MODULE_LICENSE_BSD_LIKE
     README.version
@@ -11,13 +11,3 @@
 (2) pnglibconf.h
     This is copied from scripts/pnglibconf.h.prebuilt.
     Android has undefined PNG_WARNINGS_SUPPORTED.
-
-(3) Removed contrib/testpngs/
-    There is no reason to check in all of these files if we won't
-    be using them.
-
-(4) Applied the Intel SSE patch
-    Upstream places the patch for SSE support
-    in contrib/intel/intel_sse.patch.
-    The patch was applied using the following command:
-    'patch -i contrib/intel/intel_sse.patch -p1'