Avoided some compiler warnings.

modules/juce_audio_formats/codecs/juce_AiffAudioFormat.cpp

@@ -854,7 +854,7 @@ public:
         {
             jassertfalse; // you must make sure that the window contains all the samples you're going to attempt to read.
 
-            zeromem (result, sizeof (float) * num);
+            zeromem (result, sizeof (float) * (size_t) num);
             return;
         }
 

modules/juce_audio_formats/codecs/juce_WavAudioFormat.cpp

@@ -1297,7 +1297,7 @@ public:
         {
             jassertfalse; // you must make sure that the window contains all the samples you're going to attempt to read.
 
-            zeromem (result, sizeof (float) * num);
+            zeromem (result, sizeof (float) * (size_t) num);
             return;
         }
 

modules/juce_audio_formats/format/juce_AudioFormatReader.cpp

@@ -232,7 +232,7 @@ void AudioFormatReader::readMaxLevels (int64 startSampleInFile, int64 numSamples
 
     if (numChannels < 2)
     {
-        readMaxLevels (startSampleInFile, numSamples, levels, numChannels);
+        readMaxLevels (startSampleInFile, numSamples, levels, (int) numChannels);
         levels[1] = levels[0];
     }
     else