Good, unrepresentable C strings cause errors

Error: bad argument type - not an unsigned integer: 1.23456789012346e+19

        Call history:

        compiler-tests.scm:176: print*    
        compiler-tests.scm:185: newline   
        compiler-tests.scm:188: call-with-current-continuation    
        compiler-tests.scm:188: with-exception-handler    
        compiler-tests.scm:188: ##sys#call-with-values    
        compiler-tests.scm:189: g627      
        compiler-tests.scm:190: ##sys#make-c-string       
        compiler-tests.scm:188: k619      
        compiler-tests.scm:188: g623      
        compiler-tests.scm:188: print     
        compiler-tests.scm:218: gp-test   
        compiler-tests.scm:232: expt      
        compiler-tests.scm:233: expt      
        compiler-tests.scm:232: =         
        compiler-tests.scm:238: g654      
        compiler-tests.scm:239: ##sys#foreign-unsigned-integer64-argument