Add support for input rescaling:

- round extents to power of two.
- clamp max extents.
Add output options pimpl.
Other misc API changes.

src/nvtt/CompressionOptions.cpp

@@ -87,12 +87,18 @@ void CompressionOptions::setColorWeights(float red, float green, float blue)
 }
 
 
-/// Enable or disable hardware compression.
+/// Enable or disable CUDA compression.
 void CompressionOptions::enableHardwareCompression(bool enable)
 {
 	m.useCuda = enable;
 }
 
+/// Enable or disable CUDA compression.
+void CompressionOptions::enableCudaCompression(bool enable)
+{
+	m.useCuda = enable;
+}
+
 
 /// Set color mask to describe the RGB/RGBA format.
 void CompressionOptions::setPixelFormat(uint bitcount, uint rmask, uint gmask, uint bmask, uint amask)