parser: warn when fixed-size ArrayInit doesn't have trailing {}. (#6137)

vlib/net/net.v

@@ -3,7 +3,7 @@ module net
 fn C.gethostname() int
 // hostname returns the host name reported by the kernel.
 pub fn hostname() ?string {
-	mut name := [256]byte
+	mut name := [256]byte{}
 	// https://www.ietf.org/rfc/rfc1035.txt
 	// The host name is returned as a null-terminated string.
 	namebp := byteptr(name)