Used std::ptr::null() instead of None in readme

[blwarren]

The current example in the readme produces a mismatched type error in which CreateEventW is expecting either a *const SECURITY_ATTRIBUTES or null. The error is corrected by replacing None in the example with std::ptr::null().

[kennykerr]

The repo's samples reflect the latest updates to the windows crate rather than what is available on crates.io - in other words, it is correct for the next version of the windows crate. Related: #1890

[blwarren]

Ah, I understand. I made the mistake of working from the repo readme instead of the crates.io docs. Lesson learned! Thanks!

[msyyces8x95]

@kennykerr I checked using the last version from git, it works as intended : None instead of std::ptr::null() works fine.
A genuine question, next version will break backward compatibility for 'windows' crate ? compiling old code with master branch of the crate produces some error.

Example :
code : let conf_event = CreateEventW(std::ptr::null(), true, false, None)?;
error : Error : expected enum 'Option', found *-ptr

[rylev]

Yes, the windows crate does not yet guarantee backwards compatibility between versions. The rate of change is slowing, and hopefully we'll get there soon, but we're not there yet.