Add wxLIST_DEFAULT_COL_WIDTH constant

The same value of 80px was used in both the generic and MSW versions of
wxListCtrl, so introduce a symbolic name for it and define it only once,
similarly to how it's already done for wxDVC_DEFAULT_WIDTH and
WXGRID_DEFAULT_COL_WIDTH.

No real changes.

include/wx/listbase.h

@@ -135,11 +135,12 @@ enum wxListColumnFormat
     wxLIST_FORMAT_CENTER = wxLIST_FORMAT_CENTRE
 };
 
-// Autosize values for SetColumnWidth
+// Values for SetColumnWidth()
 enum
 {
     wxLIST_AUTOSIZE = -1,
-    wxLIST_AUTOSIZE_USEHEADER = -2      // partly supported by generic version
+    wxLIST_AUTOSIZE_USEHEADER = -2,     // partly supported by generic version
+    wxLIST_DEFAULT_COL_WIDTH = 80
 };
 
 // Flag values for GetItemRect

interface/wx/listctrl.h

@@ -89,7 +89,7 @@ enum wxListColumnFormat
     wxLIST_FORMAT_CENTER = wxLIST_FORMAT_CENTRE
 };
 
-/// Autosize values for SetColumnWidth
+/// Values for SetColumnWidth()
 enum
 {
     wxLIST_AUTOSIZE = -1,

src/generic/listctrl.cpp

@@ -96,9 +96,6 @@ static const int MARGIN_BETWEEN_ROWS = 6;
 // when autosizing the columns, add some slack
 static const int AUTOSIZE_COL_MARGIN = 10;
 
-// default width for the header columns
-static const int WIDTH_COL_DEFAULT = 80;
-
 // the space between the image and the text in the report mode
 static const int IMAGE_MARGIN_IN_REPORT_MODE = 5;
 
@@ -336,7 +333,7 @@ void wxListHeaderData::SetHeight( int h )
 
 void wxListHeaderData::SetWidth( int w )
 {
-    m_width = w < 0 ? WIDTH_COL_DEFAULT : w;
+    m_width = w < 0 ? wxLIST_DEFAULT_COL_WIDTH : w;
 }
 
 void wxListHeaderData::SetState( int flag )

src/msw/listctrl.cpp

@@ -2057,7 +2057,7 @@ long wxListCtrl::DoInsertColumn(long col, const wxListItem& item)
         // always give some width to the new column: this one is compatible
         // with the generic version
         lvCol.mask |= LVCF_WIDTH;
-        lvCol.cx = 80;
+        lvCol.cx = wxLIST_DEFAULT_COL_WIDTH;
     }
 
     long n = ListView_InsertColumn(GetHwnd(), col, &lvCol);