ci: fix failing v -W build-tools and v -W build-examples; run vfmt.

examples/buf_reader.v

@@ -7,7 +7,7 @@ fn main() {
 	// Make a new connection
 	mut conn := net.dial_tcp('google.com:80') ?
 	// Simple http HEAD request for a file
-	conn.write_str('GET /index.html HTTP/1.0\r\n\r\n') ?
+	conn.write_string('GET /index.html HTTP/1.0\r\n\r\n') ?
 	// Wrap in a buffered reader
 	mut r := io.new_buffered_reader(reader: io.make_reader(conn))
 	for {

examples/net_raw_http.v

@@ -5,10 +5,10 @@ fn main() {
 	// Make a new connection
 	mut conn := net.dial_tcp('google.com:80') ?
 	defer {
-		conn.close() or { }
+		conn.close() or {}
 	}
 	// Simple http HEAD request for a file
-	conn.write_str('HEAD /index.html HTTP/1.0\r\n\r\n') ?
+	conn.write_string('HEAD /index.html HTTP/1.0\r\n\r\n') ?
 	// Read all the data that is waiting
 	result := io.read_all(reader: conn) ?
 	// Cast to string and print result

examples/path_tracing.v

@@ -106,7 +106,7 @@ fn (image Image) save_as_ppm(file_name string) {
 		c_r := to_int(unsafe { image.data[i] }.x)
 		c_g := to_int(unsafe { image.data[i] }.y)
 		c_b := to_int(unsafe { image.data[i] }.z)
-		f_out.write_str('$c_r $c_g $c_b ') or { panic(err) }
+		f_out.write_string('$c_r $c_g $c_b ') or { panic(err) }
 	}
 	f_out.close()
 }