Fix build with -Wmissing-prototypes.

Broken in 5eb4d7541107 (1.9.6), fix somehow missed in 3600bbfb43e3.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

src/core/nginx.c

diff --git a/src/core/nginx.c b/src/core/nginx.c
index cdc067e..2823169 100644
--- a/src/core/nginx.c
+++ b/src/core/nginx.c
@@ -10,7 +10,7 @@
 #include <nginx.h>
 
 
-static void ngx_show_version_info();
+static void ngx_show_version_info(void);
 static ngx_int_t ngx_add_inherited_sockets(ngx_cycle_t *cycle);
 static ngx_int_t ngx_get_options(int argc, char *const *argv);
 static ngx_int_t ngx_process_options(ngx_cycle_t *cycle);
@@ -372,7 +372,7 @@
 
 
 static void
-ngx_show_version_info()
+ngx_show_version_info(void)
 {
     ngx_write_stderr("nginx version: " NGINX_VER_BUILD NGX_LINEFEED);