Add more test cases for is_even/is_odd methods

We need to test an odd number as well as an even.

test cases/common/68 number arithmetic/meson.build

@@ -37,8 +37,10 @@ if 9 - 9 % 2 != 8
   error('Modulo precendence with subtraction is broken')
 endif
 
-assert(2.is_even(), 'int is_even() broken')
-assert(not(2.is_odd()), 'int is_odd() broken')
+assert(2.is_even(), 'int is_even() broken for even value')
+assert(not(2.is_odd()), 'int is_odd() broken for even value')
+assert(not(3.is_even()), 'int is_even() broken for odd value')
+assert(3.is_odd(), 'int is_odd() broken for odd value')
 
 assert(3 < 4, 'Lt broken')
 assert(not(4 < 3), 'Lt broken')