more vfmt fixes

vlib/strings/builder_test.v

@@ -1,5 +1,5 @@
 import strings
- 
+
 fn test_sb() {
 	mut sb := strings.Builder{}
 	sb.write('hi')
@@ -13,3 +13,22 @@ fn test_sb() {
 	assert sb.str() == 'ab'
 }
 
+const (
+	n = 100000
+)
+
+fn test_big_sb() {
+	mut sb := strings.new_builder(100)
+	for i in 0..n {
+		sb.writeln(i.str())
+	}	
+	s := sb.str()
+	lines := s.split_into_lines()
+	assert lines.len == n
+	assert lines[0] == '0'
+	assert lines[1] == '1'
+	assert lines[777] == '777'
+	assert lines[98765] == '98765'
+	
+}	
+