use ++ everywhere

vlib/strings/builder_test.v

@@ -25,7 +25,7 @@ fn test_big_sb() {
 	for i in 0..n {
 		sb.writeln(i.str())
 		sb2.write('+')
-	}	
+	}
 	s := sb.str()
 	lines := s.split_into_lines()
 	assert lines.len == n
@@ -35,8 +35,8 @@ fn test_big_sb() {
 	assert lines[98765] == '98765'
 	println(sb2.len)
 	assert sb2.len == n
-	
-}	
+
+}
 
 fn test_byte_write() {
 	mut sb := strings.new_builder(100)
@@ -44,7 +44,7 @@ fn test_byte_write() {
 	mut count := 0
 	for word in temp_str {
 		sb.write_b(word)
-		count += 1
+		count++
 		assert count == sb.len
 	}
 	assert sb.str() == temp_str