Mega Mouse support for 32X + CD (#1336)

Doom Resurrection patch version 3.0 (currently at version 3.1) added
support for the Mega Mouse, as well as making use of Mega CD hardware if
available. When I added mouse support for the Mega CD, the patch for
Doom Resurrection was at version 2.2, and since there was no licensed
32X software that supported the Mega Mouse I declined to add support at
the time. But leave it to homebrew, especially one as comprehensive as
this patch to add support.

This adds Mega Mouse support for both the 32X and 32X/CD combo, so it is
now available for all Mega * consoles.

desktop-ui/emulator/mega-32x.cpp

@@ -30,6 +30,15 @@ Mega32X::Mega32X() {
     device.digital("Start", virtualPorts[id].pad.start);
     port.append(device); }
 
+  { InputDevice device{"Mega Mouse"};
+    device.relative("X",      virtualPorts[id].mouse.x);
+    device.relative("Y",      virtualPorts[id].mouse.y);
+    device.digital ("Left",   virtualPorts[id].mouse.left);
+    device.digital ("Right",  virtualPorts[id].mouse.right);
+    device.digital ("Middle", virtualPorts[id].mouse.middle);
+    device.digital ("Start",  virtualPorts[id].mouse.extra);
+    port.append(device); }
+
     ports.append(port);
   }
 }

desktop-ui/emulator/mega-cd-32x.cpp

@@ -32,6 +32,15 @@ MegaCD32X::MegaCD32X() {
     device.digital("Start", virtualPorts[id].pad.start);
     port.append(device); }
 
+  { InputDevice device{"Mega Mouse"};
+    device.relative("X",      virtualPorts[id].mouse.x);
+    device.relative("Y",      virtualPorts[id].mouse.y);
+    device.digital ("Left",   virtualPorts[id].mouse.left);
+    device.digital ("Right",  virtualPorts[id].mouse.right);
+    device.digital ("Middle", virtualPorts[id].mouse.middle);
+    device.digital ("Start",  virtualPorts[id].mouse.extra);
+    port.append(device); }
+
     ports.append(port);
   }
 }