Support Unicode module names in wxDynamicLibrary::MSWGetModuleHandle().

The module names are not necessarily ASCII strings, so use wxString instead of
"char*" and W-version of GetModuleHandle() if appropriate.

See #15138.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73792 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Use API_VERSION_NUMBER for debug help API version check.

This symbol is not documented but seems to be defined in all the existing
versions of imagehlp.h, so use it instead of relying on a hack with checkng
whether DBHLPAPI symbol is defined.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73793 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775