[GC] Style cleanup for RewriteStatepointForGC (1 of many) [NFC]

Starting to update variable naming and types to match LLVM style.  This will be an incremental process to minimize the chance of breakage as I work.  Step one, rename member variables to LLVM CamelCase and use llvm's ADT.  Much more to come.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230042 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed