Code reorganization in PlatformDarwin for how the libdispatch
offsets structure is read & saved in the platform object -- soon
we'll be getting more than the queue name offset out of this
structure so we'll need to reuse the information in other methods.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@197620 91177308-0d34-0410-b5e6-96231b3b80d8