Add BC7 support. It's incredibly slow - ~60 seconds to compress a 512x512 image, on a Core i7 - but it works.

- Added AVPCL compressor to projects and got it building with VC9 and VC10.
- Removed unused command line interface & file read/write code from AVPCL.
- Convert AVPCL to use NV vector math lib, asserts, etc.
- Convert AVPCL to use double instead of float.
- Added 4x4 symmetric eigensolver, for AVPCL; it's based on the existing 3x3 one, but I had to rewrite the Householder reduction stage.  As with ZOH, using the eigensolver (instead of SVD) gives a ~25% speedup without significantly affecting RMSE.
- Encapsulate ZOH and AVPCL stuff into their own namespaces to keep everything separate.
- Added some missing vector operators to the nvmath lib.

src/nvtt/tools/compress.cpp

@@ -265,11 +265,10 @@ int main(int argc, char *argv[])
         {
             format = nvtt::Format_BC6;
         }
-		// !!!UNDONE: add BC7 support
-        /*else if (strcmp("-bc7", argv[i]) == 0)
+        else if (strcmp("-bc7", argv[i]) == 0)
         {
             format = nvtt::Format_BC7;
-        }*/
+        }
 
         // Undocumented option. Mainly used for testing.
         else if (strcmp("-ext", argv[i]) == 0)
@@ -355,7 +354,7 @@ int main(int argc, char *argv[])
         printf("  -bc4     \tBC4 format (ATI1)\n");
         printf("  -bc5     \tBC5 format (3Dc/ATI2)\n");
         printf("  -bc6     \tBC6 format\n");
-        //printf("  -bc7     \tBC7 format\n\n");
+        printf("  -bc7     \tBC7 format\n\n");
 
         printf("Output options:\n");
         printf("  -silent  \tDo not output progress messages\n");