MCObjectSymbolizer: Switch from IntervalMap to sorted vector, following r182625.

This removes the need for the missing SectionRef operator< workaround, and fixes
an IntervalMap assert about alignment on MSVC.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182949 91177308-0d34-0410-b5e6-96231b3b80d8