[developers] Selecting start symbols in web demo

[Stephan Oepen]

> thanks for your reply and for confirming that there is an issue.

thanks for pointing out the problem!  the functionality to adapt the
`start-symbols' setting at run-time had indeed been damaged during a
recent SVN merge across the two development branches of PET.  

i just restored that code in the CM branch and compiled new binaries
for the LOGON tree (which is what the on-line demos use).

peter, could you please cherry-pick changeset #614 into the `trunk'?

                                                        best  -  oe

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