[RFC] Add pack()/unpack() endianness modifiers for floating-point numbers

Hello everyone,

Following the recent successful vote of the RFC adding the support for
endianness modifiers on integers, I'd like to present the natural
continuation of it. It will complete the support of endianness
modifiers across relevant format letters of pack()/unpack().

Here is the RFC: https://wiki.php.net/rfc/pack-unpack-float-endianness-modifier

Thanks!

— Alexandre Daubois