Initial port of OF32S from OpenRISC-1200

There are bugs reporting by test float. Current test status (testfloat
notations):
// 1 = int32_to_float32 :DONE
// 9 = float32_to_int32 :ERROR
// 10 = float32_to_int32_round_to_zero :DONE
// 17 = float32_add :DONE
// 18 = float32_sub :DONE
// 19 = float32_mul :ERROR
// 20 = float32_div :ERROR
// 23 = float32_eq  :HANGUP
// 24 = float32_le  :HANGUP
// 25 = float32_lt  :HANGUP