Enabled -Wstrict-prototypes and fixed warnings.

src/hook.c

@@ -19,7 +19,7 @@ static seq_hooks_t hooks[HOOK_MAX];
 static malloc_mutex_t hooks_mu;
 
 bool
-hook_boot() {
+hook_boot(void) {
 	return malloc_mutex_init(&hooks_mu, "hooks", WITNESS_RANK_HOOK,
 	    malloc_mutex_rank_exclusive);
 }
@@ -100,7 +100,7 @@ for (int for_each_hook_counter = 0;					\
 }
 
 static bool *
-hook_reentrantp() {
+hook_reentrantp(void) {
 	/*
 	 * We prevent user reentrancy within hooks.  This is basically just a
 	 * thread-local bool that triggers an early-exit.