xC + frontends: merge M-! into M-a + reversed M-A

Both WeeChat and irssi merge these two by prioritising highlights
when you press M-a.

xM/main.swift

@@ -1210,7 +1210,7 @@ class WindowDelegate: NSObject, NSWindowDelegate {
 		refreshBufferList()
 	}
 
-	// Buffer indexes rotated to start after the current buffer.
+	// Buffers rotated to start after the current buffer.
 	func rotatedBuffers() -> Array<Buffer> {
 		guard let i = relayBuffers.firstIndex(
 			where: { $0.bufferName == relayBufferCurrent }) else {
@@ -1239,22 +1239,32 @@ class WindowDelegate: NSObject, NSWindowDelegate {
 		}
 	}
 
-	@objc func actionGotoHighlight() {
-		for b in rotatedBuffers() {
+	func gotoActivity(backwards: Bool) {
+		var candidates = rotatedBuffers()
+		candidates.popLast()
+		if backwards {
+			candidates.reverse()
+		}
+		for b in candidates {
 			if b.highlighted {
 				bufferActivate(name: b.bufferName)
 				return
 			}
 		}
+		for b in candidates {
+			if b.newMessages != 0 {
+				bufferActivate(name: b.bufferName)
+				return
+			}
+		}
 	}
 
 	@objc func actionGotoActivity() {
-		for b in rotatedBuffers() {
-			if b.newMessages != 0 {
-				bufferActivate(name: b.bufferName)
-				return
-			}
-		}
+		gotoActivity(backwards: false)
+	}
+
+	@objc func actionGotoBacktivity() {
+		gotoActivity(backwards: true)
 	}
 
 	@objc func actionToggleUnimportant() {
@@ -1314,12 +1324,12 @@ pushAccelerator("Switch buffer",
 
 // TODO(p): Remove .command, and ignore these with the right Option key.
 bufferMenu.addItem(NSMenuItem.separator())
-pushAccelerator("Go to highlight",
-	#selector(WindowDelegate.actionGotoHighlight),
-	"!", [.command, .option])
 pushAccelerator("Go to activity",
 	#selector(WindowDelegate.actionGotoActivity),
 	"a", [.command, .option])
+pushAccelerator("Go to activity backwards",
+	#selector(WindowDelegate.actionGotoBacktivity),
+	"a", [.shift, .command, .option])
 
 bufferMenu.addItem(NSMenuItem.separator())
 pushAccelerator("Toggle unimportant",