Remove the unnecessary virtual dtor from the DIEUnit hierarchy (in favor of protected dtor in the base, final derived classes with public non-virtual dtors)

These objects are never polymorphically owned/destroyed, so the virtual
dtor was unnecessary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301068 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed