If a comdat is dropped, all symbols in it are dropped.
If a comdat is kept, the symbols survive to pass regular symbol
resolution.
With this patch we do that for all global symbols.
The added test is a copy of test/tools/gold/X86/comdat.ll that we now
pass.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@264192 91177308-0d34-0410-b5e6-96231b3b80d8
