Unasserted runtime_error? calls in test cases

[tueda]

Currently, there are several runtime_error? without assertions:

grep '^runtime' -rn check

check/features.frm:1510:runtime_error?("Illegal attempt for strict rounding without activating floating point numbers.")
check/features.frm:1511:runtime_error?("Forgotten #startfloat instruction?")
check/features.frm:1512:runtime_error?("Illegal argument(s) in StrictRounding statement: ''")
check/features.frm:1513:runtime_error?("Illegal argument(s) in StrictRounding statement: 'd5'")
check/features.frm:1514:runtime_error?("Illegal argument(s) in StrictRounding statement: ',d'")
check/features.frm:1661:runtime_error?("Illegal use of a transform statement and float_")
check/features.frm:1662:runtime_error?("Illegal use of a transform statement and float_")
check/features.frm:1663:runtime_error?("Illegal use of a transform statement and float_")
check/features.frm:1664:runtime_error?("Illegal use of a transform statement and float_")
check/features.frm:2278:runtime_error?("Illegal parameter in #StartFloat: 100bd,MZV = 10")
check/features.frm:2287:runtime_error?("Error: Weight of Euler/MZV sum greater than 2.")
check/features.frm:2288:runtime_error?("Please increase the maximum weight in #startfloat.")
check/features.frm:2297:runtime_error?("Divergent MZV in CalculateMZV")
check/features.frm:2306:runtime_error?("Illegal index[0] in CalculateMZV: -2")
check/features.frm:2315:runtime_error?("Illegal index[1] in CalculateMZVhalf: -1")
check/features.frm:2324:runtime_error?("Divergent Euler sum in CalculateEuler")