This has the nice side-effect that it can actually store the quadruple version numbers that Apple's tools are using nowadays.
rdar://82982162
Differential Revision: https://reviews.llvm.org/D111200
If the debug info is missing the terminating null die, we would crash
when trying to access the nonexisting children/siblings. This was
discovered because the test case for D98619 accidentaly produced such
input.