Revert "Removed platforms from preSolution which are not AnyCPU"

This reverts commit 3b12088.

Author: Chris Jakeman

Source/ORTS.sln

@@ -56,7 +56,11 @@ EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
+		Debug|Mixed Platforms = Debug|Mixed Platforms
+		Debug|x64 = Debug|x64
 		Release|Any CPU = Release|Any CPU
+		Release|Mixed Platforms = Release|Mixed Platforms
+		Release|x64 = Release|x64
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
 		{9BE44F64-417D-4AA6-AF4D-2A6A0CBC814D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU