There are now four ways that CBT can be disabled:
1. Network-wide, with the cbtdisabled consensus param.
2. Via config, with "LearnCircuitBuildTimeout 0"
3. Via config, with "AuthoritativeDirectory 1"
4. Via a state file write failure.
This just got a little complicated, since old clients use "clipped
advertised bandwith" and new clients now use "consensus bandwidth" but
fall back to "clipped advertised bandwidth".
Fix several bugs in computing recommended versions. 1) refactor is-this-version-good handling and which-vesions-are-good handling to be in the same place. 2) a version is recommended if more than half of the versioning authorities like it, not >= half. 3) "NEW_IN_SERIES" should mean, "I don't know of an 0.1.1.x this recent, and there are some 0.1.2.x versions out", not "I don't know of an 0.1.1.x this recent, but I know some older ones." This should resolve bug 383.
svn:r9523
Write the entry guards section of path-spec; note a possible bug in cirbuitbuild.c; add a const; defer work on torrc.complete to be part of a bigger config documentation reorg.
svn:r9465
