fixed_debug.h: delete some dead code

this has the side-effect of removing some C++ style comments

Signed-off-by: Jean-Marc Valin <jmvalin@jmvalin.ca>

celt/fixed_debug.h

@@ -238,9 +238,6 @@ static OPUS_INLINE int SHL32_(opus_int64 a, int shift, char *file, int line)
 #define HALF16(x)  (SHR16(x,1))
 #define HALF32(x)  (SHR32(x,1))
 
-//#define SHR(a,shift) ((a) >> (shift))
-//#define SHL(a,shift) ((a) << (shift))
-
 #define ADD16(a, b) ADD16_(a, b, __FILE__, __LINE__)
 static OPUS_INLINE short ADD16_(int a, int b, char *file, int line)
 {