merge upstream and fix CMake build
Please review the merge conflict resolutions carefully, especially in libAACdec/src/aacdecoder.cpp
and libAACdec/src/aacdecoder_lib.cpp
. I am not familiar with this code. Both the autotools and CMake builds are working. Encoding and decoding with https://github.com/mixxxdj/mixxx/pull/3543 worked in my brief test.