Make Ctrl+A not work in multiline wxTextCtrl in MSW

The native EDIT control doesn't handle this key combination, but RICHEDIT does
and people just expect it to work, so handle it at wxMSW level.

Closes https://github.com/wxWidgets/wxWidgets/pull/300

docs/changes.txt

@@ -150,6 +150,7 @@ wxMSW:
   methods return wxAccStatus::wxACC_NOT_SUPPORTED.
 - Return null BSTR from wxIAccessible if string returned from wxAccesible
   method is empty.
+- Handle Ctrl-A in non-rich multiline text controls (Jens Göpfert).
 
 wxOSX:
 

src/msw/textctrl.cpp

@@ -2054,13 +2054,26 @@ void wxTextCtrl::OnKeyDown(wxKeyEvent& event)
         }
     }
 
-    // Default window procedure of multiline edit controls posts WM_CLOSE to
-    // the parent window when it gets Escape key press for some reason, prevent
-    // it from doing this as this resulted in dialog boxes being closed on
-    // Escape even when they shouldn't be (we do handle Escape ourselves
-    // correctly in the situations when it should close them).
-    if ( event.GetKeyCode() == WXK_ESCAPE && IsMultiLine() )
-        return;
+    if ( IsMultiLine() )
+    {
+        // Default window procedure of multiline edit controls posts WM_CLOSE to
+        // the parent window when it gets Escape key press for some reason, prevent
+        // it from doing this as this resulted in dialog boxes being closed on
+        // Escape even when they shouldn't be (we do handle Escape ourselves
+        // correctly in the situations when it should close them).
+        if ( event.GetKeyCode() == WXK_ESCAPE )
+            return;
+
+        // We also handle Ctrl-A as the native EDIT control doesn't do it by
+        // default (but RICHEDIT one does, so there is no need to check for it
+        // in the switch above), however it's a de facto standard accelerator
+        // and people expect it to work.
+        if ( event.GetModifiers() == wxMOD_CONTROL && event.GetKeyCode() == 'A' )
+        {
+            SelectAll();
+            return;
+        }
+    }
 
     // no, we didn't process it
     event.Skip();