Add xfixes feature

[conqp]

• [*] Tested on an x11 machine
• [*] Compilation warnings were addressed
• [*] cargo fmt has been run on this branch
• [*] cargo doc builds successfully
• [*] Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• [*] Updated documentation to reflect any user-facing changes
• [-] Created or updated an example program if it would help users understand this functionality

Fixes https://github.com/AltF02/x11-rs/pull/159

[AltF02]

Released at https://crates.io/crates/x11/2.20.1