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)

apps/nseq.c

diff --git a/apps/nseq.c b/apps/nseq.c
index 018d5eb..a97fe18 100644
--- a/apps/nseq.c
+++ b/apps/nseq.c
@@ -18,7 +18,7 @@
     OPT_TOSEQ, OPT_IN, OPT_OUT
 } OPTION_CHOICE;
 
-OPTIONS nseq_options[] = {
+const OPTIONS nseq_options[] = {
     {"help", OPT_HELP, '-', "Display this summary"},
     {"toseq", OPT_TOSEQ, '-', "Output NS Sequence file"},
     {"in", OPT_IN, '<', "Input file"},