[DWARF] Have HashedNameToDIE store a DataExtractor by value
[DWARF] Have HashedNameToDIE store a DataExtractor by value

Summary:
The DataExtractors are cheap to copy so there is no reason to store them
by reference. Also, in my upcoming indexing refactor I am planning to
remove the apple tables data extractor members from the SymbolFileDWARF
class, so there will not be a DataExtractor with a suitable lifetime to
refer to.

Reviewers: clayborg, JDevlieghere

Subscribers: aprantl, lldb-commits

Differential Revision: https://reviews.llvm.org/D46888

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@332596 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb,llvm-mirror/lldb