roll libyuv from r1610 to r1616

Fix for ltcg on VS2012 and earlier - extern declspec must match declaration.
Fixes suggested by mozilla for android/mozilla warnings.
SplitUVPlane and MergeUVPlane functions to allow lighter weight chroma conversions for NV12 and NV21 to/from I420.

Change log:
https://chromium.googlesource.com/libyuv/libyuv/+log/74491ba0..de944ed8
https://chromium.googlesource.com/libyuv/libyuv/+/74491ba0..de944ed8

Includes a fix for ltcg on VS2013 and earlier.

BUG=libyuv:633,libyuv:630,libyuv:629,libyuv:626,libyuv:631

Review-Url: https://codereview.chromium.org/2291283002
Cr-Commit-Position: refs/heads/master@{#415427}

DEPS

@@ -228,7 +228,7 @@ deps = {
     Var('chromium_git') + '/external/github.com/open-source-parsers/jsoncpp.git' + '@' + 'f572e8e42e22cfcf5ab0aea26574f408943edfa4', # from svn 248
 
   'src/third_party/libyuv':
-    Var('chromium_git') + '/libyuv/libyuv.git' + '@' + '74491ba0c508efaa99aeb95c53c618a694ac57f6',
+    Var('chromium_git') + '/libyuv/libyuv.git' + '@' + 'de944ed8c74909ea6fbd743a22efe1e55e851b83',
 
   'src/third_party/smhasher/src':
     Var('chromium_git') + '/external/smhasher.git' + '@' + 'e87738e57558e0ec472b2fc3a643b838e5b6e88f',