Add ifdef to headers

AudioConvert_F32.h

@@ -1,6 +1,6 @@
 
-#ifndef _AudioConvert_I16toF32
-#define _AudioConvert_I16toF32
+#ifndef _AudioConvert_I16toF32_h
+#define _AudioConvert_I16toF32_h
 
 
 #include <AudioStream_F32.h>

AudioEffectGain_F32.h

@@ -9,6 +9,9 @@
  * MIT License.  use at your own risk.
 */
 
+#ifndef _AudioEffectGain_h
+#define _AudioEffectGain_h
+
 #include <arm_math.h> //ARM DSP extensions.  for speed!
 #include <AudioStream_F32.h>
 
@@ -51,3 +54,4 @@ class AudioEffectGain_F32 : public AudioStream_F32
     float gain = 1.0; //default value
 };
 
+#endif

AudioFilterFIR_F32.h

@@ -6,8 +6,8 @@
  * 
  */
 
-#ifndef _filter_fir_f32
-#define _filter_fir_f32
+#ifndef _filter_fir_f32_h
+#define _filter_fir_f32_h
 
 #include "Arduino.h"
 #include "AudioStream_F32.h"