Add missing extern "C"

OpenAL32/Include/sample_cvt.h

@@ -4,6 +4,10 @@
 #include "AL/al.h"
 #include "alBuffer.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 extern const ALshort muLawDecompressionTable[256];
 extern const ALshort aLawDecompressionTable[256];
 
@@ -12,4 +16,8 @@ void Convert_ALshort_ALima4(ALshort *dst, const ALubyte *src, ALsizei numchans,
 void Convert_ALshort_ALmsadpcm(ALshort *dst, const ALubyte *src, ALsizei numchans, ALsizei len,
                                ALsizei align);
 
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
 #endif /* SAMPLE_CVT_H */