LibAudio: Modernize WAV loader

With this, the WAV loader is a completely modern LibAudio loader:
- Own type header for RIFF data structures
- custom stream read functions for the types
- Final removal of legacy I/O error checking
- clearer error messages
- clean handling of header chunks

The latter will allow proper handling of other chunks (before "data") in
the future, such as metadata :^)

Userland/Libraries/LibAudio/CMakeLists.txt

@@ -2,6 +2,7 @@ set(SOURCES
     GenericTypes.cpp
     SampleFormats.cpp
     Loader.cpp
+    RIFFTypes.cpp
     WavLoader.cpp
     FlacLoader.cpp
     WavWriter.cpp