Separate the "interface specification" into multiple individual, shorter
pages. Also update some outdated parts and replace references to
OpenBeOS with Haiku.
Change-Id: I86baa9a78c5f7a8a3c4c7aa3ac2992714afecae6
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6084
Tested-by: Automation <automation@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
