Test more values in is-prime sub

This covers incorrect values described in RT#127044 https://rt.perl.org/Ticket/Display.html?id=127044

Author: zoffixznet

S32-num/is-prime.t

@@ -43,4 +43,9 @@ for (0, 32416187771, 32416187772, 32416187775) -> $composite {
 
 ok  170141183460469231731687303715884105727.is-prime, "170141183460469231731687303715884105727 is prime";
 nok 170141183460469231731687303715884105725.is-prime, "170141183460469231731687303715884105725 is not prime";
-ok 6864797660130609714981900799081393217269435300143305409394463459185543183397656052122559640661454554977296311391480858037121987999716643812574028291115057151.is-prime, "M13 is prime";
+ok 6864797660130609714981900799081393217269435300143305409394463459185543183397656052122559640661454554977296311391480858037121987999716643812574028291115057151.is-prime, "M13 is prime";
+
+ok  is-prime(2.0),   "correct coersion (Rat)";
+ok  is-prime('2.0'), "correct coersion (Str)";
+nok is-prime(2.5),   "decimal numbers are not prime";
+nok isprime(-2),     "negative numbers are not prime";