Fix debug-info-alias test to add CHECK to some lines that were missing it.

To simplify source location offsets, this test uses line directives to
force particular lines of interest to have known line numbers so that
adjustments before/after those points don't require updates to the CHECK
lines.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207779 91177308-0d34-0410-b5e6-96231b3b80d8