Use WXK_DELETE as Unicode key code for VK_DELETE in wxMSW.

U+007F is a Unicode character so we should set Unicode key code to this value
for VK_DELETE presses. This also makes wxMSW consistent with wxGTK.

Closes #3458.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73718 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Initialize Unicode code when generating wxEVT_CHAR_HOOK in wxMSW.

Use the fixed value of 0 for the keys without Unicode equivalent instead of
whatever junk was there in the uninitialized variable.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73719 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Add wxDocument::Activate() method.

Make activating the first (and, in the vast majority of cases, the only) view
of the document easier.

Closes #15120.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73720 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775