Run interprocedural const prop before global optimizer

Run interprocedural const prop before global optimizer

Exposes more constant globals that can be removed by
the global optimizer. A specific example is the removal
of the static global block address array in
clang/test/CodeGen/indirect-goto.c. This change impacts only
lower optimization levels. With LTO interprocedural
const prop runs already before global opt.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@212284 91177308-0d34-0410-b5e6-96231b3b80d8