Fix some paths, notably in includes of the terrain-graphics directory.

These inclusions were redundant to the C++ code, which pulls that 
file in early in the process of interpreting the WML tree.  But
they're actually needed by tools like wmlunits that don't start 
with the topmost _main.cfg.

data/campaigns/Descent_Into_Darkness/utils/terrain.cfg

@@ -1,4 +1,6 @@
 # Door-related terrain and macros ########################################
+{core/terrain-graphics/}
+
 [terrain]
     symbol_image=flat/road
     id=door
@@ -10,4 +12,4 @@
     recruit_from=false
     editor_group=did
 [/terrain]
-{TERRAIN_BASE xx flat/road}
+{TERRAIN_BASE xx flat/road}

data/campaigns/Two_Brothers/scenarios/3_Guarded_Castle.cfg

@@ -8,7 +8,7 @@
     aliasof=Xu
 [/terrain]
 
-{terrain-graphics}
+{core/terrain-graphics/}
 {TERRAIN_BASE Xzga flat/road}
 
 [scenario]

data/campaigns/Under_the_Burning_Suns/utils/terrain.cfg

@@ -1,6 +1,8 @@
 #textdomain wesnoth-utbs
 # Special terrains I use in the UTBS maps
 
+{core/terrain-graphics/}
+
 # dark tile terrain
 # for this to work for some reason it has to be on the top of the list
 

data/campaigns/Under_the_Burning_Suns/utils/terrain_graphics.cfg

@@ -2,7 +2,7 @@
 # A supplementary terrain-graphics file
 # which is supposed to help with transitions
 
-{terrain-graphics}
+{core/terrain-graphics/}
 {./adjacent_custom.cfg}
 
 # These three take care that no transitions of dirt, road etc are drawn over the

data/core/units.cfg

@@ -28,7 +28,7 @@
     {core/units/undead/}
     {core/units/wose/}
     {core/units/fake/}
-    {~units}
+    {~units/}
 
     #traits that are common to all races and units
     {TRAIT_STRONG}