Fixed RtlCompareString and RtlCompareStringN, they were very wrong, for CompareString the params are struct ptrs not char ptrs

Fixed a ton of clang-cl compiler warnings about unused variables, still many left. Fixed a lot of inconsistent override ones too

src/xenia/base/filesystem_win.cc

@@ -149,7 +149,7 @@ class Win32FileHandle : public FileHandle {
       return false;
     }
   }
-  bool SetLength(size_t length) {
+  bool SetLength(size_t length) override {
     LARGE_INTEGER position;
     position.QuadPart = length;
     if (!SetFilePointerEx(handle_, position, nullptr, SEEK_SET)) {

src/xenia/base/split_map.h

@@ -67,8 +67,6 @@ class split_map {
   void InsertAt(TKey k, TValue v, uint32_t idx) {
     uint32_t old_size = size();
 
-    bool needs_shiftup = idx != old_size;
-
     values_.insert(values_.begin() + idx, v);
     keys_.insert(keys_.begin() + idx, k);
   }