Extend the dumping infrastructure to deal with additional

Extend the dumping infrastructure to deal with additional
sections for debug info. These are some of the dwo sections from the
DWARF5 split debug info proposal. Update the fission-cu.ll testcase
to show what we should be able to dump more of now.

Work in progress: Ultimately the relocations will be gone for the
dwo section and the strings will be a different form (as well as
the rest of the sections will be included).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171428 91177308-0d34-0410-b5e6-96231b3b80d8