Rework of runtime non-real-time threading, and shared object dynamic loading :
- All exposed operations on PLCObject are now serialized through main thread
(@RunInMain). Only one exception : python trace thread calling _GetDebugData
- Re-loading of same shared object is prevented. dlclose/delte/rewrite/dlopen
don't happen in that case. This is a workaround for some xenomai copperplate
bug triggering segfault, inbetween delete and rewrite.
- Trace thread now waits for data, dies if no data, and dies instead of
suspending as before when no data consumed after 3 seconds.
- Disabled threading in Pyro client
- Enforced auxiliary threads starting sequence : Pyro -> [UI] ->
PLCWorker.RunLoop

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<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            xmlns:xhtml="http://www.w3.org/1999/xhtml">
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        <xsd:any namespace="http://www.w3.org/1999/xhtml" processContents="lax"/>
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</xsd:schema>