Alert user to drop-outs during recording...

1) When the program detects this, insert zeroes into the recording to keep the
other good parts synchronized.

2) When recording stops, a message box alerts the user, and a label track is
added showing the lost parts, labelled with consecutive numbers.

3) A menu item visible in alpha builds only is added to Tools, to simulate
recording errors at random times and test the reporting feature.

src/RingBuffer.cpp

@@ -75,6 +75,27 @@ size_t RingBuffer::Put(samplePtr buffer, sampleFormat format,
    return copied;
 }
 
+size_t RingBuffer::Clear(sampleFormat format, size_t samplesToClear)
+{
+   samplesToClear = std::min( samplesToClear, AvailForPut() );
+   size_t cleared = 0;
+   auto pos = mEnd;
+
+   while(samplesToClear) {
+      auto block = std::min( samplesToClear, mBufferSize - pos );
+
+      ClearSamples(mBuffer.ptr(), format, pos, block);
+
+      pos = (pos + block) % mBufferSize;
+      samplesToClear -= block;
+      cleared += block;
+   }
+
+   mEnd = pos;
+
+   return cleared;
+}
+
 //
 // For the reader only:
 //