[MetaHook] Load DTX texture to OpenGL

This function load a LithTech *.dtx texture file and convert to OpenGL pixel format, compressed support.

Use FileSystem interface. :D

 #pragma pack(1)

 struct DtxHeader
 {
     unsigned int iResType;
     int iVersion;
     unsigned short usWidth;
     unsigned short usHeight;
     unsigned short usMipmaps;
     unsigned short usSections;
     int iFlags;
     int iUserFlags;
     unsigned char ubExtra[];
     char szCommandString[];
 };

 #pragma pack()

 bool LoadDTX(const char *pszFileName, unsigned char *pBuffer, int iBufferSize, int *pInternalFormat, int *pWidth, int *pHeight, int *pImageSize)
 {
     FileHandle_t pFile = g_pFileSystem->Open(pszFileName, "rb");

     if (!pFile)
         return false;

     DtxHeader Header;
     memset(&Header, , sizeof(Header));

     g_pFileSystem->Read(&Header, sizeof(Header), pFile);

     if (Header.iResType !=  || Header.iVersion != - || Header.usMipmaps == )
     {
         g_pFileSystem->Close(pFile);
         return false;
     }

     *pWidth = Header.usWidth;
     *pHeight = Header.usHeight;

     int iBpp = Header.ubExtra[];
     int iSize;

     if (iBpp == )
         iBpp = ;

     if (iBpp == )
     {
         iSize = Header.usWidth * Header.usHeight * ;
         *pInternalFormat = GL_RGBA;
     }
     else if (iBpp == )
     {
         iSize = (Header.usWidth * Header.usHeight) >> ;
         *pInternalFormat = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
     }
     else if (iBpp == )
     {
         iSize = Header.usWidth * Header.usHeight;
         *pInternalFormat = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
     }
     else if (iBpp == )
     {
         iSize = Header.usWidth * Header.usHeight;
         *pInternalFormat = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
     }
     else
     {
         iSize = ;
     }

     *pImageSize = iSize;

     if (iSize ==  || iSize > iBufferSize)
     {
         g_pFileSystem->Close(pFile);
         return false;
     }

     g_pFileSystem->Read(pBuffer, iSize, pFile);

     if (iBpp == )
     {
         for (uint32 i = ; i < (uint32)iSize; i += )
         {
             pBuffer[i + ] ^= pBuffer[i + ];
             pBuffer[i + ] ^= pBuffer[i + ];
             pBuffer[i + ] ^= pBuffer[i + ];
         }
     }

     g_pFileSystem->Close(pFile);
     return true;
 }