Fix compile error with --enable-maintainer-mode

hdtest/comp_helper.c

@@ -24,7 +24,7 @@
  */
 #include "comp_helper.h"
 
-void dump_val(json_t *jent, const char *key, uint8_t *val, size_t len)
+static void dump_val(json_t *jent, const char *key, uint8_t *val, size_t len)
 {
   if(val == NULL) {
     json_object_set_new(jent, key, json_string("**DEALLOCATED**"));

hdtest/inflatehd.c

@@ -101,7 +101,7 @@ static int inflate_hd(json_t *obj, nghttp2_hd_context *inflater, int seq)
   return 0;
 }
 
-static int perform()
+static int perform(void)
 {
   nghttp2_hd_context inflater;
   size_t i;

lib/nghttp2_hd.c

@@ -97,7 +97,7 @@ static nghttp2_hd_entry static_table[] = {
   /* 58 */ MAKE_NV("www-authenticate", "")
 };
 
-const static size_t STATIC_TABLE_LENGTH =
+static const size_t STATIC_TABLE_LENGTH =
   sizeof(static_table)/sizeof(static_table[0]);
 
 typedef struct {