Remove unused function.
Simplify cxa_atexit(), first part.

Remove trigger__cxa_atexit(), we will just remap until successful.
Remove unused dso parameter.
Instead of friending just provide a function.
Pass a transaction, the typesafe way.
Keep trying to remap __cxa_atexit until succeeded.

__cxa_atexit is generated by clang::CodeGen upon seeing the first static
destructor. Instead of trying to provoke that we just continue to search for it.
Dealy running static init until gCling is defined; local_cxa_atexit() needs it.
Move some code around to chop Interpreter() into smaller pieces.
First step away from SVN versioning.