Extended RTOnce with termination cleanups. (Changes existing structures and functions.)
IPRT: Inlined the already-done check in RTOnce().
RTOnce: Avoid allocating anything when there are no races.
Automated rebranding to Oracle copyright/license strings via filemuncher
*: s/RT_\(BEGIN|END\)_DECLS/RT_C_DECLS_\1/g
iprt/*: __BEGIN_DECLS -> RT_BEGIN_DECLS; __END_DECLS -> RT_END_DECLS.
IPRT: Added a RTOnceReset method (needed it for a testcase).
IPRT: Implemented the RTOnce API.