実数(倍精度)型の境界条件の値を読み込む。
call cg_iric_read_bc_real(fid, type, num, name, value, ier)
ier = cg_iRIC_Read_BC_Real(fid, type, num, name, &value);
value = cg_iRIC_Read_BC_Real(fid, type, num, name)