Add DEBUG constant for both Debug and Debug-COM25

Allows for only requiring #if DEBUG if debug code can apply to both.

Directory.Build.props

@@ -10,6 +10,7 @@
   </PropertyGroup>
 
   <PropertyGroup Condition=" $(Configuration.StartsWith('Debug')) ">
+    <DefineConstants>DEBUG</DefineConstants> 
     <DebugSymbols>true</DebugSymbols>
     <Optimize>false</Optimize>
   </PropertyGroup>
@@ -20,7 +21,7 @@
   </PropertyGroup>
 
   <PropertyGroup Condition=" $(Configuration.EndsWith('COM25')) ">
-    <DefineConstants>COM25</DefineConstants>
+    <DefineConstants>$(DefineConstants);COM25</DefineConstants>
   </PropertyGroup>
 
   <ItemGroup>