objectSize in objectImpl.c is not used thread safe

The global variable objectSize in objcetImpl.c is not used thread save. It is used for a hack, where objects are used within string buffers.

This bug affects at least parallel invoke method calls within one provider process. But there may be more situations.

How to reproduce:
Run multiple Indication Providers that fire inidcations rapidly in parallel. The bug will produce a segfault in the InteropProvider Process when _deliver is invoked.

Solution:
Do not pass the objectSize with a global variable. Instead change the method signatures.

Please see the attached patch, that introduces a new argument length to the addClString and replaceClString methods. The methods are renamed to avoid conflicts with calls to the original methods.