Fix overlap check in rdcarray::insert

This fixes an infinite when attempting to call `insert(0, NULL, 0)`
on an empty `rdcarray`.

The new behaviour also triggers a copy when the inserted interval
overlaps the `rdcarray`'s *allocated* memory (rather than just the
currently used prefixed).

Change-Id: I075827d50a24d0560ca391224820334e467a41f5

renderdoc/api/replay/basic_types.h

@@ -439,7 +439,7 @@ public:
 
   void insert(size_t offs, const T *el, size_t count)
   {
-    if(el + count >= begin() && end() >= el)
+    if(elems < el + count && el < elems + allocatedCount)
     {
       // we're inserting from ourselves, so if we did this blindly we'd potentially change the
       // contents of the inserted range while doing the insertion.