Add an ability to pack to single-precision floats

[rybakit]

$packer = new Packer(Packer::FORCE_FLOAT); // Packer::FORCE_DOUBLE
...
$packer->packFloat(3.14);
$packer->packDouble(3.14);

or

$packer = new Packer(Packer::FORCE_FLOAT32); // Packer::FORCE_FLOAT64
...
$packer->packFloat32(3.14);
$packer->packFloat64(3.14);