added tests for float and rat types (all big endian). Changed if-elseif chains to atomic ifs for better error reporting.
added tests for float and rat types (all big endian). Changed if-elseif chains to atomic ifs for better error reporting.

porridge/goexif,op/goexif,bdotdub/goexif,kladd/goexif,rwcarlsen/goexif,xor-gate/goexif2,junjizhi/goexif,hydnwang/goexif