message: restored memset optimization
  when dropping optimizations in the last commit, I forgot to keep the
  simplest case where a single memset can be called
diff: @@ -1076,6 +1076,10 @@ static inline void ICV_HLINE_X(uchar* ptr, int xl, int xr, const uchar* color, i
  uchar* hline_min_ptr = (uchar*)(ptr) + (xl)*(pix_size);
  uchar* hline_end_ptr = (uchar*)(ptr) + (xr+1)*(pix_size);
  uchar* hline_ptr = hline_min_ptr;
  + if (pix_size == 1)
  + memset(hline_min_ptr, *color, hline_end_ptr-hline_min_ptr);
  + else//if (pix_size != 1)
  + {
  if (hline_min_ptr < hline_end_ptr)
  {
  memcpy(hline_ptr, color, pix_size);
  @@ -1088,6 +1092,7 @@ static inline void ICV_HLINE_X(uchar* ptr, int xl, int xr, const uchar* color, i
  hline_ptr += sizeToCopy;
  sizeToCopy = std::min(2*sizeToCopy, static_cast<size_t>(hline_end_ptr-hline_ptr));
  }//end while(hline_ptr < hline_end_ptr)
  + }//end if (pix_size != 1)
  }
  //end ICV_HLINE_X()
  