Unexpected behaviour of print(char, HEX) and print(int, HEX)

```
char c = 255;
Serial.print(c, HEX);
```

produces

```
FFFFFFFF
```

This is due to the fact that `print(char c, int base)` convert char c (1 byte) into an unsigned long (4 bytes). As char is signed 255 is in fact -1(Two's complement), once written in 4 bytes it becomes FFFFFFFF. But as a user I would rather have FF than FFFFFFFF.

The problem exist with int (2 bytes) too

Here is a more complete example:

```
void setup() {
Serial.begin(9600);
int i = 1;
Serial.print("i: ");
Serial.print(i, 10);
Serial.print(" | ");
Serial.println(i, HEX);
i = -1;
Serial.print("i: ");
Serial.print(i, 10);
Serial.print(" | ");
Serial.println(i, HEX);

char c = 127;
Serial.print("c: ");
Serial.print(c, 10);
Serial.print(" | ");
Serial.println(c, HEX);
c = 255;
Serial.print("c: ");
Serial.print(c, 10);
Serial.print(" | ");
Serial.println(c, HEX);
}

void loop() {}
```

output

```
i: 1 | 1
i: -1 | FFFFFFFF
c: 127 | 7F
c: -1 | FFFFFFFF
```

where I owuld rather have

```
i: 1 | 1
i: -1 | FFFF
c: 127 | 7F
c: -1 | FF
```

まず、issue で説明されている Serial.print(char c, int base) と Serial.print(int, int base) のオーバーロードを見つけ、次に完全なサンプルスケッチを実行して出力を再現します。-1 を int とした場合は FFFF、-1 を char とした場合は FF を生成するように、16 進数出力がオペランドの幅を使用し、既存の 10 進数出力が維持されれば完了です。

索引モデルが issue の本文から書いたものです。