Error handling fix in xmltree. Fixes a problem where if the start of the
stream is spread over two packets (or SSL records in this case), xt_handle()
would report a fatal error (which normally means the connection has failed
and should be abandoned immediately).
Returning 1 is likely more correct; just the fact that there's no data to
process yet is not a fatal failure.
This fixes potential issues with Google Talk when using OpenSSL (which
seems to be feeding data on record boundaries, even if additional records
have already been received).
