XRC spec: document the "focused" window property.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74922 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
XRC spec: document the "title" property for wxWizard.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74923 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
XRC spec: relax requirements on some commonly omitted properties.

Some properties documented as required, such as labels on wxStaticText
or wxCheckBox or the size of wxSizer spacers, are frequently omitted in
practice.

Rather than strictly requiring them, forcing the markup to include dummy
empty elements, loosen the restriction in the spec and make them
optional.  Nothing changes about actual acceptance of files by
wxXmlResource: it would already silently deal with the lack of these
properties.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74924 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
XRC spec: document wxRibbon* XRC handler.

Format documentation was nonexistent (the few words present were
incorrect). Document my best guess about the intended usage.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74925 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Misc validity fixes to samples/xrc/rc/*.xrc.

Fix invalid XRC markup.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74926 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Add RELAX NG schema for XRC files.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74927 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775