TST: Use repr in byteswapping tests
TST: Use repr in byteswapping tests

The `str` values for those weird values used for longdouble are
truncated by PyPy's complex `str` output.  Which seems fine probably
since PyPy's `repr` does the right thing and will not truncate.

rgommers/numpy,pdebuyl/numpy,numpy/numpy,endolith/numpy,mattip/numpy,jakirkham/numpy,charris/numpy,endolith/numpy,charris/numpy,pdebuyl/numpy,mattip/numpy,numpy/numpy,charris/numpy,rgommers/numpy,jakirkham/numpy,mhvk/numpy,rgommers/numpy,pdebuyl/numpy,jakirkham/numpy,mattip/numpy,endolith/numpy,numpy/numpy,seberg/numpy,mhvk/numpy,anntzer/numpy,anntzer/numpy,charris/numpy,rgommers/numpy,seberg/numpy,seberg/numpy,seberg/numpy,mhvk/numpy,jakirkham/numpy,mattip/numpy,numpy/numpy,mhvk/numpy,endolith/numpy,jakirkham/numpy,mhvk/numpy,anntzer/numpy,pdebuyl/numpy,anntzer/numpy