Remove svnrev.cs from repo and just assume it's there

Reverts 4e5f7e40e. In hindsight this was the obvious, easy solution to the error
in fresh clones. For the record, VS will still complain that the class is
missing on a fresh clone *before compiling*, but now the first compile will
succeed as well as subsequent compiles.

Version/Version.csproj

@@ -8,6 +8,9 @@
 		<PlatformTarget>AnyCPU</PlatformTarget>
 		<TargetFramework>netstandard2.0</TargetFramework>
 	</PropertyGroup>
+	<ItemGroup>
+		<Compile Include="svnrev.cs" /><!-- Not checked-in, but needs to be added to the compile list which is generated before the pre-build event, so this will make MSBuild pretend it's there when cloning. -->
+	</ItemGroup>
 	<Target Name="Build">
 		<!-- when is this called? it's never run and failed on Linux -->
 		<Exec Command="&quot;$(MSBuildProjectDirectory)\subwcrev.bat&quot; $(MSBuildProjectDirectory)" Condition=" '$(OS)' == 'Windows_NT' " WorkingDirectory="$(MSBuildProjectDirectory)" />

Version/svnrev.cs

@@ -1 +0,0 @@
-// This file will get overwritten by a pre-build target defined in Version.csproj.