<rdar://problem/13125225>

Adding data formatters for std::set, std::multiset and std::multimap for libc++
The underlying data structure is the same as std::map, so this change is very minimal and mostly consists of test cases



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@183323 91177308-0d34-0410-b5e6-96231b3b80d8