libcxxrt: don't export nonexistant symbols

[brooks]

Summary

Remove version entries that we don't build.

Add an arm specific Version.map and for other targets run the files
through sed to handle int vs long in new and delete.

Ideally we'd use the SYMBOL_MAPS functionality to preproces with cpp,
but it doesn't currently handle C++ symbols so be annoyingly duplicative
for now.

[brooks]

These changes to Version.map aren't optimal, but they work in that they allow building with WITHOUT_UNDEFINED_VERSION defined and I've used my symbol level ABI checker (D44271) to verify that no symbols were lost.