redox: Export UDS, resource, syslog, and others

[joshuamegnauth54]

What does this PR do

I exported a few supported Redox features: resource.h, syslog, and some fcntl.h constants. Some of these changes only work on libc's main branch as I only recently enabled them there too which is why I'm keeping this as a draft.

Checklist:

• [x] I have read CONTRIBUTING.md
• [x] I have written necessary tests and rustdoc comments
• [x] A change log has been added if this PR modifies nix's API

[jackpot51]

@joshuamegnauth54 is this ready?