libvpx: Pull from upstream

Current HEAD: 7ec7a33a081aeeb53fed1a8d87e4cbd189152527

git log from upstream:
7ec7a33a0 Release v1.8.2 Pekin Duck

Test: upstream

Change-Id: If7ab690a76b3cd93a3c922d5e9fc9a3996668005
diff --git a/README.version b/README.version
index fd2dc9c..cc2c2a3 100644
--- a/README.version
+++ b/README.version
@@ -1,5 +1,6 @@
-URL: https://chromium.googlesource.com/webm/libvpx/+archive/v1.8.1.tar.gz
-Version: v1.8.1
+URL: https://chromium.googlesource.com/webm/libvpx/+archive/v1.8.2.tar.gz
+Version: v1.8.2
 BugComponent: 42195
 Owners: johannkoenig
 Local Modifications:
+  652beb6ac trivial: fix spelling errors