GetCurrentSelection() was documented but not present in all ports (just MSW and GTK); moved it to the base classes

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42727 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/latex/wx/combobox.tex

@@ -191,6 +191,16 @@ Copies the selected text to the clipboard.
 Copies the selected text to the clipboard and removes the selection.
 
 
+\membersection{wxComboBox::GetCurrentSelection}\label{wxcomboboxgetcurrentselection}
+
+\constfunc{int}{GetCurrentSelection}{\void}
+
+This function does the same things as 
+\helpref{wxChoice::GetCurrentSelection}{wxchoicegetcurrentselection} and
+returns the item currently selected in the dropdown list if it's open or the
+same thing as \helpref{GetSelection}{wxcontrolwithitemsgetselection} otherwise.
+
+
 \membersection{wxComboBox::GetInsertionPoint}\label{wxcomboboxgetinsertionpoint}
 
 \constfunc{long}{GetInsertionPoint}{\void}