Port folder renaming changes from AOM

Manually cherry-picked commits:
ceef058 libvpx->libaom part2
3d26d91 libvpx -> libaom
cfea7dd vp10/ -> av1/
3a8eff7 Fix a build issue for a test
bf4202e Rename vpx to aom

Change-Id: I1b0eb5a40796e3aaf41c58984b4229a439a597dc

test/y4m_video_source.h

@@ -15,7 +15,7 @@
 #include "test/video_source.h"
 #include "./y4minput.h"
 
-namespace libvpx_test {
+namespace libaom_test {
 
 // This class extends VideoSource to allow parsing of raw yv12
 // so that we can do actual file encodes.
@@ -117,6 +117,6 @@ class Y4mVideoSource : public VideoSource {
   y4m_input y4m_;
 };
 
-}  // namespace libvpx_test
+}  // namespace libaom_test
 
 #endif  // TEST_Y4M_VIDEO_SOURCE_H_