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
diff --git a/ivfenc.c b/ivfenc.c
index a50d318..b1e0f77 100644
--- a/ivfenc.c
+++ b/ivfenc.c
@@ -10,8 +10,8 @@
 
 #include "./ivfenc.h"
 
-#include "vpx/vpx_encoder.h"
-#include "vpx_ports/mem_ops.h"
+#include "aom/vpx_encoder.h"
+#include "aom_ports/mem_ops.h"
 
 void ivf_write_file_header(FILE *outfile, const struct vpx_codec_enc_cfg *cfg,
                            unsigned int fourcc, int frame_cnt) {