Fix wxRegKey::GetKeyInfo() output parameters in 64 bit builds.

Fix wxRegKey::GetKeyInfo() output parameters in 64 bit builds.

Use intermediate 32 bit DWORD variables for ::RegQueryInfoKey() outputs as
size_t is 64 bit in 64 bit MSW builds and so the variables of type size_t
can't/shouldn't be passed directly to this function to avoid only filling
their lower 32 bits.

Closes #11778.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67246 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775