Fix lldb-mi test data_read_memory_bytes_global
Test was skipped because -data-evaluate-expression was thought
to not work on globals. This is not the case - the issue was clang
removes debug info for globals in cpp files that are not used.
Add a reference to the globals in question, and fix memory patter in
test to match memory pattern in testcase.
Reviewers: ki.stfu, abidh
Reviewed By: ki.stfu
Subscribers: aprantl, lldb-commits
Differential Revision: https://reviews.llvm.org/D37533