Deal with the consequences of constifying getters

Reviewed-by: Stephen Henson <steve@openssl.org>
Reviewed-by: Emilia Käsper <emilia@openssl.org>
diff --git a/apps/apps.c b/apps/apps.c
index fca3775..ec1cfe9 100644
--- a/apps/apps.c
+++ b/apps/apps.c
@@ -1148,7 +1148,7 @@
     }
 }
 
-void print_bignum_var(BIO *out, BIGNUM *in, const char *var,
+void print_bignum_var(BIO *out, const BIGNUM *in, const char *var,
                       int len, unsigned char *buffer)
 {
     BIO_printf(out, "    static unsigned char %s_%d[] = {", var, len);