COW cleanup patch (1583966):

1. perform deep comparison for the classes for which it makes sense in the
   ports where this wasn't done yet
2. remove (shallow) comparison operators for the classes for which it does
   not make sense (such as wxBitmap)
3. makes wxBitmap use COW on all ports
4. adds wxObject::IsRefTo()
5. centralizes and improves COW docs


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42752 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/latex/wx/object.tex

@@ -116,6 +116,13 @@ this one or is derived from it.
   bool tmp = obj->IsKindOf(CLASSINFO(wxFrame));
 \end{verbatim}
 
+\membersection{wxObject::IsRefTo}\label{wxobjectisrefto}
+
+\func{bool}{IsRefTo}{\param{const wxObject *}{ obj}}
+
+Returns \true if this object is referencing the \arg{obj}'s data.
+Note that this function only does a {\tt shallow} comparison.
+
 \membersection{wxObject::Ref}\label{wxobjectref}
 
 \func{void}{Ref}{\param{const wxObject\& }{clone}}
@@ -165,6 +172,17 @@ The {\bf m\_refData} member is set to NULL.
 \helpref{wxObject::SetRefData}{wxobjectsetrefdata}, \helpref{wxObject::GetRefData}{wxobjectgetrefdata},\rtfsp
 \helpref{wxObjectRefData}{wxobjectrefdata}
 
+\membersection{wxObject::UnShare}\label{wxobjectunshare}
+
+\func{void}{UnShare}{\void}
+
+Ensure that this object's data is not shared with any other object.
+
+if we have no
+data, it is created using CreateRefData() below, if we have shared data
+it is copied using CloneRefData(), otherwise nothing is done.
+
+
 \membersection{wxObject::operator new}\label{wxobjectnew}
 
 \func{void *}{new}{\param{size\_t }{size}, \param{const wxString\& }{filename = NULL}, \param{int}{ lineNum = 0}}