New implementation of log2udp

- optional line numbering
- optional line prefix
- fire-and-forget mode (ignore network errors)
- coalesces lines into packets with configurable timeout
- fixed footprint

+ bugfix: make circular output queue actually circular
+ bugfix: check against the right edge of the buffer
+ add:    delimiter between fields now configurable
+ fix:    Rejigger whitespace (4 spaces, no hard tabs)
+ bugfix: handle prefix and delim neatly to avoid
          potential buffer overflows from commandline
+ tweak:  ignore ECONNREFUSED if ignore_net_errs
          (work around kernel "feature")
+ add:    .gitreview

Change-Id: I4f39d696503fd9399c360902ebf21a7ad39fe649