ref_counter typedef conflicts with persistent_data::ref_counter

[ilyakurdyukov]

In persistent-data/data-structures/array.h:

	template <typename ValueTraits>
	class array : public array_base {
	public:
		class block_ref_counter : public ref_counter<uint64_t> {
		public:

		typedef typename ValueTraits::ref_counter ref_counter;

The ambiguity here is whether the ref_counter name refers to persistent_data::ref_counter or ValueTraits::ref_counter from the later typedef.

This gives errors when using compilers based on EDG frontend, and their developers think your code is wrong, not the compiler.

Possible solution:

-		class block_ref_counter : public ref_counter<uint64_t> {
+		class block_ref_counter : public persistent_data::ref_counter<uint64_t> {

It's better not to use the same name everywhere.

[jthornber]

I just pushed your fix. Thank you.