verify encoding on windows; fixup a few warnings

include/libnyquist/PostProcess.h

@@ -87,7 +87,7 @@ void StereoToMono(const T * src, T * dest, size_t N)
 template <typename T>
 void MonoToStereo(const T * src, T * dest, size_t N)
 {
-    for(int i = 0, j = 0; i < N; ++i, j += 2)
+    for(size_t i = 0, j = 0; i < N; ++i, j += 2)
     {
         dest[j] = src[i];
         dest[j + 1] = src[i];

src/OpusDecoder.cpp

@@ -95,7 +95,7 @@ public:
         
         while(0 < framesRemaining)
         {
-            int64_t framesRead = op_read_float(fileHandle, buffer, (int)(framesRemaining * d->channelCount), nullptr);
+            auto framesRead = size_t(op_read_float(fileHandle, buffer, (int)(framesRemaining * d->channelCount), nullptr));
             
             // EOF
             if(!framesRead)

src/WavPackDecoder.cpp

@@ -56,7 +56,7 @@ public:
         auto totalSamples = size_t(getTotalSamples());
         
         int mode = WavpackGetMode(context);
-        int isFloatingPoint = (MODE_FLOAT & mode);
+        bool isFloatingPoint = (MODE_FLOAT & mode);
         
         d->sourceFormat = MakeFormatForBits(bitdepth, isFloatingPoint, false);