Fix confusion with LOGFONT{A,W} parameters to MSW GetTheme[Sys]Font().

Fix confusion with LOGFONT{A,W} parameters to MSW GetTheme[Sys]Font().

Change the signature of GetThemeFont() and GetThemeSysFont() methods of
wxUxThemeEngine to take an artificial wxUxThemeFont::Ptr type instead of
LOGFONT which allows the broken code to compile correctly and even work in
Unicode builds but crashed in ANSI ones under Windows Vista/7 as these
functions expect a LOGFONTW and not LOGFONTA even in non-Unicode build under
these systems.

This generalizes the previous fix/workaround for the same problem in
wxStaticBox so remove it now and use wxUxThemeFont both there and in
wxMenuItem to avoid crashes when using owner-drawn menus in ANSI build.

Closes #12364.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65955 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775