Fix wxMenu::GetTitle() before the menu is appended to the menu bar.

The mnemonics conversion was not done correctly when the menu title contained
them but the menu hadn't been appended to the menu bar yet.

Closes #15461.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74731 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix infinite loop in wxMSW with wxStaticBox inside non-wxTAB_TRAVERSAL parent.

We didn't ensure that the parent of a (native) control with WS_EX_CONTROLPARENT
had this style as well, unlike for our own windows. Fix this now to make
certain that we never call ::IsDialogMessage() on a window whose parent
doesn't have WS_EX_CONTROLPARENT as it simply hangs in this case, entering an
infinite loop searching for the default button.

Also try to reduce the possibility of such bugs in the future by checking for
WS_EX_CONTROLPARENT and not wxTAB_TRAVERSAL before calling ::IsDialogMessage()
even if this doesn't totally prevent them (it wasn't sufficient to fix even
this particular bug).

Closes #15458.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74732 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775