Create new line while pressing enter in repl.

Pressing Enter in repl should create new line instead of quiting the repl.

compiler/main.v

@@ -858,7 +858,11 @@ fn run_repl() []string {
 	mut lines := []string
 	for {
 		print('>>> ')
-		mut line := os.get_line().trim_space()
+		mut line := os.get_raw_line()
+		if line.trim_space() == '' && line.ends_with('\n') {
+			continue
+		}
+		line = line.trim_space()
 		if line == '' {
 			break
 		}

os/os.v

@@ -383,6 +383,17 @@ pub fn get_line() string {
 	return tos(buf, nr_chars)
 }
 
+// get_raw_line returns a one-line string from stdin along with '\n' if there is any
+pub fn get_raw_line() string {
+	max := u64(256)
+	buf := malloc(int(max))
+	nr_chars := C.getline(&buf, &max, stdin)
+	if nr_chars == 0 {
+		return ''
+	}
+	return tos(buf, nr_chars)
+}
+
 pub fn user_os() string {
 	$if linux {
 		return 'linux'