[C++11] More 'nullptr' conversion. In some cases just using a boolean check instead of comparing to nullptr.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206142 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/ArrayRecycler.h

@@ -44,10 +44,10 @@ class ArrayRecycler {
   // Return NULL if no entries are available.
   T *pop(unsigned Idx) {
     if (Idx >= Bucket.size())
-      return 0;
+      return nullptr;
     FreeList *Entry = Bucket[Idx];
     if (!Entry)
-      return 0;
+      return nullptr;
     Bucket[Idx] = Entry->Next;
     return reinterpret_cast<T*>(Entry);
   }