[PATCH nftables] src/main.c: fix build with gcc <= 4.8

[Fabrice Fontaine <fontaine.fabrice@gmail.com>]

Since commit 719e44277f8e89323a87219b4d4bc7abac05b051, build with
gcc <= 4.8 fails on:

main.c:186:2: error: 'for' loop initial declarations are only allowed in C99 mode
  for (size_t i = IDX_INTERACTIVE + 1; i < NR_NFT_OPTIONS; ++i)
  ^

Fixes:
 - http://autobuild.buildroot.org/results/cf2359b8311fe91f9335c91f2bb4a730c9f4c9dc

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
---
 src/main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/main.c b/src/main.c
index d830c7a2..e248a347 100644
--- a/src/main.c
+++ b/src/main.c
@@ -169,6 +169,7 @@ static void print_option(const struct nft_opt *opt)
 
 static void show_help(const char *name)
 {
+	size_t i;
 	printf("Usage: %s [ options ] [ cmds... ]\n"
 	       "\n"
 	       "Options:\n", name);
@@ -185,7 +186,7 @@ static void show_help(const char *name)
 
 	fputs("\n", stdout);
 
-	for (size_t i = IDX_INTERACTIVE + 1; i < NR_NFT_OPTIONS; ++i)
+	for (i = IDX_INTERACTIVE + 1; i < NR_NFT_OPTIONS; ++i)
 		print_option(&nft_options[i]);
 
 	fputs("\n", stdout);
-- 
2.26.2