Improve <D-w> behaviour

With this patch <D-w> works as follows:
- if in Ex-mode, exit by sending "^U:vi<CR>"
- if the command-line window is open, close it using CTRL-\_CTRL-N
- otherwise go to normal mode and add ":q<CR>" to the input buffer

src/MacVim/MMBackend.m

@@ -1648,6 +1648,24 @@ static NSString *MMSymlinkWarningString =
         [self handleOdbEdit:data];
     } else if (XcodeModMsgID == msgid) {
         [self handleXcodeMod:data];
+    } else if (CloseMsgID == msgid) {
+        // If in Ex mode, then simply exit Ex mode (^U:vi<CR>).  Otherwise
+        // try to close one (Vim-)window by going to Normal mode first
+        // (CTRL-\_CTRL-N) and then sending ":q<CR>", but only if the
+        // command-line window is not open.  If the command-line window is open
+        // then we just go back to normal mode (since CTRL-\_CTRL-N closes the
+        // command-line window).
+        if (exmode_active) {
+            // Exit Ex mode
+            add_to_input_buf((char_u*)"\x15:vi\n", 5);
+        } else {
+            // Go to normal mode
+            add_to_input_buf((char_u*)"\x1c\xe", 2);
+            if (0 == cmdwin_type) {
+                // Command-line window was not open, so :q
+                add_to_input_buf((char_u*)":q\n", 3);
+            }
+        }
     } else {
         NSLog(@"WARNING: Unknown message received (msgid=%d)", msgid);
     }

src/MacVim/MMWindowController.m

@@ -593,11 +593,9 @@
 
 - (IBAction)performClose:(id)sender
 {
-    // NOTE: File->Close is bound to this action message instead binding it
-    // directly to the below vim input so that File->Close also works for
-    // auxiliary windows such as the About dialog.  (If we were to bind the
-    // below, then <D-w> will not close e.g. the About dialog.)
-    [vimController addVimInput:@"<C-\\><C-N>:conf q<CR>"];
+    // NOTE: File->Close is bound to this action message so that File->Close
+    // also works for auxiliary windows such as the About dialog.
+    [vimController sendMessage:CloseMsgID data:nil];
 }
 
 - (IBAction)findNext:(id)sender

src/MacVim/MacVim.h

@@ -162,6 +162,7 @@ enum {
     LiveResizeMsgID,
     EnableAntialiasMsgID,
     DisableAntialiasMsgID,
+    CloseMsgID,
 };
 
 

src/MacVim/MacVim.m

@@ -75,6 +75,7 @@ char *MessageStrings[] =
     "LiveResizeMsgID",
     "EnableAntialiasMsgID",
     "DisableAntialiasMsgID",
+    "CloseMsgID",
 };