Added some more helper functions for serialization of CVSRevision.
This commit also changes next_timestamp and prev_timestamp to
fixed-width hex representation, in agreement with design-notes.txt.
* cvs2svn (CVSRevision.__str__): Use local helper functions
timestamp_to_string(), rev_to_string(), and list_to_string() to help
with serialization.
(parse_cvs_revision): Use local helper functions
string_to_timestamp() and string_to_rev() to help with
deserialization.
git-svn-id: http://cvs2svn.tigris.org/svn/cvs2svn/trunk@1846 be7e6eca-30d4-0310-a8e5-ac0d63af7087