Move wxGetLibraryVersionInfo() to core from base.

Move wxGetLibraryVersionInfo() to core from base.

This function uses the GUI toolkit information and so can't be defined in
wxBase. The code only compiled before because the function was erroneously
defined in wxCore even though it was declared as WXDLLIMPEXP_BASE.

Fix this by declaring it with WXDLLIMPEXP_CORE too. This corrects problems in
MSW DLL build.

If we need to get a string containing user-readable wxBase version too, we
should add another function (as it's not possible to virtualize this one) but
such function doesn't seem incredibly useful to have anyhow.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@66493 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775