Cycles: Fix issues with stack allocator in MSVC

Couple of issues here:

- Was a bug in heap memory allocation when run out
  of allowed stack memory.

- Debug MSVC was failing because it uses separate
  allocator for some sort of internal proxy thing,
  which seems to be unable to be using stack memory
  because allocator is being created in non-persistent
  stack location.

intern/cycles/util/util_stack_allocator.h

@@ -40,14 +40,17 @@ public:
 	/* Allocator construction/destruction. */
 
 	StackAllocator()
-	: pointer_(0) {}
+	: pointer_(0),
+	  use_stack_(true) {}
 
 	StackAllocator(const StackAllocator&)
-	: pointer_(0) {}
+	: pointer_(0),
+	  use_stack_(true) {}
 
 	template <class U>
 	StackAllocator(const StackAllocator<SIZE, U>&)
-	: pointer_(0) {}
+	: pointer_(0),
+	  use_stack_(false) {}
 
 	/* Memory allocation/deallocation. */
 
@@ -57,7 +60,7 @@ public:
 		if(n == 0) {
 			return NULL;
 		}
-		if(pointer_ + n >= SIZE) {
+		if(pointer_ + n >= SIZE || use_stack_ == false) {
 			size_t size = n * sizeof(T);
 			util_guarded_mem_alloc(size);
 			T *mem;
@@ -69,6 +72,7 @@ public:
 			if(mem == NULL) {
 				throw std::bad_alloc();
 			}
+			return mem;
 		}
 		T *mem = &data_[pointer_];
 		pointer_ += n;
@@ -157,6 +161,7 @@ public:
 
 private:
 	int pointer_;
+	bool use_stack_;
 	T data_[SIZE];
 };