fix comment in C file

src/SIEVE03.c

@@ -3,9 +3,13 @@
 #define LIMIT 10000
 #define PRIMES 1000
 
-// Sieve of Eratosthenes
-// Author: Greg Gauthier
-// Date: 2016-01-20
+/* Sieve of Eratosthenes
+ * Author: Greg Gauthier
+ * Date: 2016-01-20
+ * NOTE: cannot use single-line comments in these C files because
+ *       of the fact that the MVS SYSIN is interpreting them as
+ *       JCL operands.
+*/
 int main()
 {
    int i,j,numbers[LIMIT];