Add some unit tests for StringExtractor::GetNameColonValue.
Add some unit tests for StringExtractor::GetNameColonValue.

These are helpful on their own, but will be even more useful
once the GetNameColonValue is updated to return StringRefs
instead of std::strings.

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@279919 91177308-0d34-0410-b5e6-96231b3b80d8

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