Change "vp8" to "aom"

aom/aom_codec.mk

aom/src/svc_encodeframe.c

aom/svc_context.h

aom/vp8.h

aom/vp8cx.h

aom/vp8dx.h

aom_dsp/bitreader.h

aomdec.c

aomenc.c

av1/av1_cx_iface.c

av1/av1_dx_iface.c

av1/encoder/encoder.h

examples/aom_temporal_svc_encoder.c

examples/decode_to_md5.c

examples/decode_with_drops.c

examples/set_maps.c

libs.mk

test/codec_factory.h

test/decode_api_test.cc

test/encode_api_test.cc