qHash of QHash fails to compile on gcc

The qHash of QHash table doesn't compile on linux under gcc (version 10 or any modern)

e.g.: for QHash<int, int> a;

qHash(a) fails to compile.

The problem is following:

In qhash.h (line 1445) the hash commutative combiner is called with std :: pair<const Key&, const T&>. In example above it's std :: pair<const int&, const int&>.

In qhashfunctions.h (line 139 - 140) QHashCombineCommutative::operator() calls qHash with the std :: pair<const Key&, const T&>. However qHash for std :: pair is defined AFTER on line 167.
So that it conforms to C++ standard this must be defined (or at least declared) BEFORE.
Fix is to move this above QHashCombineCommutative.