Fix DXT1a support.

src/nvtt/CompressDXT.cpp

@@ -241,7 +241,7 @@ void nv::compressDXT1a(const Image * image, const OutputOptions::Private & outpu
 			rgba.init(image, x, y);
 			
 			// Compress color.
-			squish::ColourSet colours((uint8 *)rgba.colors(), 0);
+			squish::ColourSet colours((uint8 *)rgba.colors(), squish::kDxt1|squish::kWeightColourByAlpha);
 			squish::WeightedClusterFit fit(&colours, squish::kDxt1);
 			fit.setMetric(compressionOptions.colorWeight.x(), compressionOptions.colorWeight.y(), compressionOptions.colorWeight.z());
 			fit.Compress(&block);

src/nvtt/squish/colourset.cpp

@@ -27,6 +27,12 @@
 
 namespace squish {
 
+// @@ Add flags:
+// - FindColorMatch
+// - DXT1a
+// - WeightColorByAlpha
+
+	
 ColourSet::ColourSet( u8 const* rgba, int flags )
   : m_count( 0 ), 
 	m_transparent( false )