Made the MP random map generator be included explicitly for the editor...

...so that the editor doesn't need to set the MULTIPLAYER symbol. Also
made the editor include the UMC campaigns dir, so that UMC can make
their custom terrains available to the editor.

data/_main.cfg

@@ -3,29 +3,38 @@
 
 {core/}
 
-#The editor needs the multiplayer included since the random maps are defined there
-{multiplayer/}
+#ifdef MULTIPLAYER
+    {multiplayer/}
+#endif
+
 #ifdef EDITOR
-[textdomain]
-    name="wesnoth-editor"
-[/textdomain]
+    [textdomain]
+        name="wesnoth-editor"
+    [/textdomain]
+    
+    # The editor needs to know of the default multiplayer random map generator
+    {multiplayer/scenarios/Random_Scenario.cfg}
+    
+    # This enables UMC to define their custom terrains inside an EDITOR ifdef,
+    # so the terrains become available in the editor by default
+    {~campaigns/}
 #else
-{campaigns/}
-{scenario-test.cfg}
-{scenario-formula.cfg}
-[textdomain]
-    name="wesnoth"
-[/textdomain]
-[textdomain]
-    name="wesnoth-units"
-[/textdomain]
-[textdomain]
-    name="wesnoth-multiplayer"
-[/textdomain]
-# required  to wire it in rather early, won't work in the ifdef for the tutorial
-[textdomain]
-    name="wesnoth-tutorial"
-[/textdomain]
+    {campaigns/}
+    {scenario-test.cfg}
+    {scenario-formula.cfg}
+    [textdomain]
+        name="wesnoth"
+    [/textdomain]
+    [textdomain]
+        name="wesnoth-units"
+    [/textdomain]
+    [textdomain]
+        name="wesnoth-multiplayer"
+    [/textdomain]
+    # required  to wire it in rather early, won't work in the ifdef for the tutorial
+    [textdomain]
+        name="wesnoth-tutorial"
+    [/textdomain]
 #endif
 
 [binary_path]

data/multiplayer/_main.cfg

@@ -12,9 +12,7 @@
     {DEFAULT_MUSIC_PLAYLIST}
 [/generic_multiplayer]
 
-#ifdef MULTIPLAYER
 {multiplayer/scenarios/}
 {~scenarios/multiplayer/}
-#endif
 
 {multiplayer/eras.cfg}

src/editor/editor_main.cpp

@@ -279,10 +279,6 @@ int main(int argc, char** argv)
 
 	defines_map["MEDIUM"] = preproc_define();
 	defines_map["NORMAL"] = preproc_define();
-	// Multiplayer define is needed to access the random map generator
-	// settings. Maybe they should be moved? Or set an EDITOR define and
-	// make it load that way maybe.
-	defines_map["MULTIPLAYER"] = preproc_define();
 
 #if defined(__APPLE__)
 	defines_map["APPLE"] = preproc_define();