Constify char* input parameters in apps code

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>

test/ssltest_old.c

diff --git a/test/ssltest_old.c b/test/ssltest_old.c
index 8863465..6a5cd70 100644
--- a/test/ssltest_old.c
+++ b/test/ssltest_old.c
@@ -954,7 +954,7 @@
 
 int main(int argc, char *argv[])
 {
-    char *CApath = NULL, *CAfile = NULL;
+    const char *CApath = NULL, *CAfile = NULL;
     int badop = 0;
     enum { BIO_MEM, BIO_PAIR, BIO_IPV4, BIO_IPV6 } bio_type = BIO_MEM;
     int force = 0;