Initialise c->clipped_timestamp when loading single contigs in the
older database format.

Without this we could generate random timestamps and so sometimes use
a cached (zero length) contig size when the cache wasn't valid,
leading to truncated contigs from Save Consensus (and elsewhere).

This only happened when using the newer gap5 on a database built with
the older tg_index.


git-svn-id: https://staden.svn.sourceforge.net/svnroot/staden/staden/trunk@3104 ba6f2710-ca9f-427c-89d3-5bf716dbc8e1