coreaudio: modern C++

- replace malloc by C++ vector or new[]
- use unique_ptr for dynamic allocations
- use C++ cast than C cast
- do not copy, use const&, & or move-idiom
- replace NULL by nullptr
- AAA rule
- general coding rules

Change-Id: I8a62ca9ef59b0807d5abeb0a5090521843dbb9ca