Executables may not contain a load config, and clients should be able to
test for nullability. Previously we'd return uninitialized memory. Now
getLoadConfig32/64 return valid pointers or null.
Fixes PR34108
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@310308 91177308-0d34-0410-b5e6-96231b3b80d8