[dsymutil] Accept line tables up to DWARFv5.

This patch removes the hard-coded check for DWARFv2 line tables. Now
dsymutil accepts line tables for DWARF versions 2 to 5 (inclusive).

Differential revision: https://reviews.llvm.org/D41084

rdar://35968319

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320469 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed