Change SystemRuntimeMacOSX::ReadLibdispatchTSDIndexes to use the
ProcessStructReader instead of reading the structure out of libdispatch
by hand.  I will convert more of the struct readers in SystemRuntimeMacOSX
over to use this class eventually.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@217649 91177308-0d34-0410-b5e6-96231b3b80d8