Fix comments. Minor fixes.

src/nvtt/Context.cpp

@@ -321,7 +321,9 @@ bool Compressor::Private::compress(const InputOptions::Private & inputOptions, c
 
             if (img.isNormalMap()) {
                 if (inputOptions.normalizeMipmaps) {
+                    img.expandNormals();
                     img.normalizeNormalMap();
+                    img.packNormals();
                 }
                 tmp = img;
             }

src/nvtt/nvtt.h

@@ -102,10 +102,9 @@ namespace nvtt
         Format_DXT1n,   // Not supported.
         Format_CTX1,    // Not supported.
 
-        Format_BC6,     // Not supported yet.
-        Format_BC7,     // Not supported yet.
+        Format_BC6,
+        Format_BC7,
 
-        //Format_BC5_Luma,    // Two DXT alpha blocks encoding a single float.
         Format_BC3_RGBM,    // 
 
         Format_Count