[SabreAMF] Improvement of SabreAMF_AMF3_Serializer::writeInt

[Develar]

1000 iterations, 0.018 vs 0.0827

public function writeInt($int)
	{
		$bytes = array();
		if (($int & 0xff000000) == 0)
		{
			for ($i = 3; $i > -1; $i--)
			{
				$bytes[] = ($int >> (7 * $i)) & 0x7F;
			}
		}
		else
		{
			for ($i = 2; $i > -1; $i--)
			{
				$bytes[] = ($int >> (8 + 7 * $i)) & 0x7F;
			}
			$bytes[] = $int & 0xFF;
		}

		for ($i = 0; $i < 3; $i++)
		{
			if ($bytes[$i] == 0)
			{
				unset($bytes[$i]);
			}
			else
			{
				$this->stream->writeByte($bytes[$i] | 0x80);
			}
		}
		$this->stream->writeByte($bytes[3]);
	}