AudioCore: Skeleton Implementation

This commit:
* Adds a new subproject, audio_core.
* Defines structures that exist in DSP shared memory.
* Hooks up various other parts of the emulator into audio core.

This sets the foundation for a later HLE DSP implementation.

src/audio_core/CMakeLists.txt

@@ -0,0 +1,16 @@
+set(SRCS
+            audio_core.cpp
+            hle/dsp.cpp
+            hle/pipe.cpp
+            )
+
+set(HEADERS
+            audio_core.h
+            hle/dsp.h
+            hle/pipe.h
+            sink.h
+            )
+
+create_directory_groups(${SRCS} ${HEADERS})
+
+add_library(audio_core STATIC ${SRCS} ${HEADERS})