[codeview] Fix inline line table accuracy for discontiguous segments

After improving the inline line table dumper in llvm-pdbutil and looking
at MSVC's inline line tables, it is clear that setting the length of the
inlined code region does not update the code offset. This means that the
delta to the beginning of a new discontiguous inlined code region should
be calculated relative to the last code offset, excluding the length.
Implementing this is a one line fix for MC: simply don't update
LastLabel.

While I'm updating these test cases, switch them to use llvm-objdump -d
and llvm-pdbutil. This allows us to show offsets of each instruction and
correlate the line table offsets to the actual code.

llvm-svn: 362264