Allow Tor to be compiled without support for relay mode
Let's make some more optional modules.
Our target set of modules might include:
- dirauth - the code only used by directory authorities (including bridge authorities)
- dircache - the code only used by directory caches and directory authorities
- relay - the code only used by relays and directory authorities
- common - the code used by all roles
I'll do a design, and a proposed CI build strategy, and then get it reviewed.