[DWARF] Refactoring range list dumping to fold DWARF v4 functionality into v5 handling

Eliminating some duplication of rangelist dumping code at the expense of
some version-dependent code in dump and extract routines.

Reviewer: dblaikie, JDevlieghere, vleschuk

Differential revision: https://reviews.llvm.org/D51081

llvm-svn: 342048