Repair the coercion of C string literals to C++ strings for function arguments: must create a copy for non-const arguments and can use C++ coercion for const literals.
Closes #2132.

extend C++ tests to make sure we do not generate warnings (and fix some warnings that we did generate)

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extra : amend_source : 6a5e7668208a89296264b05bbfe7640514318a1d

rewrite of sliced char* decoding as utility functions, implemented efficient sliced decoding for C++ std::string

--HG--
extra : rebase_source : e134f5595be98eb990ab2195e8208940efb171fe