Also, move SFmode code to immediately after DFmode code.
(S_MODES, D_MODES): Handle XFmode.
(XF_MODES): Was TF_MODES, handle XFmode instead of TFmode.
(hard_regno_mode_ok): Replace TFmode with XFmode.
(i960_output_long_double): New function.

From-SVN: r9738