Added mg_mmap and mg_munmap utility functions for memory mapping files

Added mg_mmap and mg_munmap utility functions for memory mapping files
if (fh != INVALID_HANDLE_VALUE)
{
  HANDLE mh = CreateFileMapping(fh, 0, PAGE_READONLY, 0, 0, 0);
  if(mh)
   {
     .....
   } 
  else
   {
    DBG (("Error CreateFileMapping %d",GetLastError() ));
   }
}
else
{
   DBG (("Error _get_osfhandle %d", GetLastError()));
}