Constify command options

Reviewed-by: Kurt Roeckx <kurt@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1694)
diff --git a/apps/cms.c b/apps/cms.c
index 21f0961..306e159 100644
--- a/apps/cms.c
+++ b/apps/cms.c
@@ -84,7 +84,7 @@
     OPT_CIPHER
 } OPTION_CHOICE;
 
-OPTIONS cms_options[] = {
+const OPTIONS cms_options[] = {
     {OPT_HELP_STR, 1, '-', "Usage: %s [options] cert.pem...\n"},
     {OPT_HELP_STR, 1, '-',
         "  cert.pem... recipient certs for encryption\n"},