port of redo-c to BetterC

[aquaratixc]

Good day! This is my first time working with betterC and for the 
sake of experiment I decided to translate the redo-c 
implementation (https://github.com/leahneukirchen/redo-c) into 
BetterC, but I ran into a number of problems:
1. In the original implementation, there are places where the 
openat function is used (dir_fd, target, O_RDONLY | O_DIRECTORY); 
and I couldn't find a replacement. Are there any options where 
you can get it?
2. Similarly, the dprintf function was not found, which, as I 
understand it, is a non-standard extension. Is there a way to add 
this?
I will also be glad if someone picks up the idea and brings it to 
mind. The current version is here: 
https://github.com/aquaratixc/redo-d/tree/main