Disable the StringMapEntry copy constructor, to make sure we
reject things like: "for (auto Entry : SomeStringMap)".  Previously
this would copy the value but not the tail allocated string data
(the key).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182713 91177308-0d34-0410-b5e6-96231b3b80d8