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

vlib/os/os.v

@@ -89,7 +89,7 @@ pub fn cp(old, new string) ? {
 			C.close(fp_from)
 			return error_with_code('cp: failed to write to $new', int(fp_to))
 		}
-		mut buf := [1024]byte
+		mut buf := [1024]byte{}
 		mut count := 0
 		for {
 			// FIXME: use sizeof, bug: 'os__buf' undeclared

vlib/os/os_nix.c.v

@@ -141,7 +141,7 @@ pub fn exec(cmd string) ?Result {
 	if isnil(f) {
 		return error('exec("$cmd") failed')
 	}
-	buf := [4096]byte
+	buf := [4096]byte{}
 	mut res := strings.new_builder(1024)
 	for C.fgets(charptr(buf), 4096, f) != 0 {
 		bufbp := byteptr(buf)

vlib/os/os_windows.c.v

@@ -264,7 +264,7 @@ pub fn exec(cmd string) ?Result {
 		h_std_error: child_stdout_write
 		dw_flags: u32(C.STARTF_USESTDHANDLES)
 	}
-	command_line := [32768]u16
+	command_line := [32768]u16{}
 	C.ExpandEnvironmentStringsW(cmd.to_wide(), voidptr(&command_line), 32768)
 	create_process_ok := C.CreateProcessW(0, command_line, 0, 0, C.TRUE, 0, 0, 0, voidptr(&start_info), voidptr(&proc_info))
 	if !create_process_ok {
@@ -274,7 +274,7 @@ pub fn exec(cmd string) ?Result {
 	}
 	C.CloseHandle(child_stdin)
 	C.CloseHandle(child_stdout_write)
-	buf := [4096]byte
+	buf := [4096]byte{}
 	mut bytes_read := u32(0)
 	mut read_data := strings.new_builder(1024)
 	for {