Update docstrings. No functional change.

* serf.h, serf_bucket_types.h, serf_bucket_util.h:
   Update existing docstrings, mostly adding @since references for 1.4
   versions. Reformatted some strings and added Doxygen markup on others.


git-svn-id: https://svn.apache.org/repos/asf/serf/trunk@1842251 13f79535-47bb-0310-9956-ffa450edef68
3 files changed