Promise constification.
cf3parse.y: make comma-after-promiser message more helpful
Add RingBuffer

Basic ring buffer. We can add more functionality as needed later.
Not thread safe, perhaps add read/write lock later, but this should
be specified in constructor in that case.
Constify Promise under OS X
Merge pull request #1204 from sigurdteigen/master

Add RingBuffer
Merge pull request #1199 from tzz/feature/clarify-comma-after-promiser-error

cf3parse.y: make comma-after-promiser message more helpful
Add RingBufferHead/Tail
Accumulate messages in PromiseLogging
Merge pull request #1192 from jimis/Promise_constification

Promise constification.