For CI - use AppVeyor CI image with VS 2017.

[skip travis] [ci only: master]

.appveyor.yml

@@ -21,6 +21,7 @@
 #
 
 version: '{build}'
+image: Visual Studio 2017
 platform:
   - x86
   - x64
@@ -70,7 +71,12 @@ before_build:
           $env:URHO3D_TOOLS = "0";
           iex ((new-object net.webclient).DownloadString('https://raw.githubusercontent.com/appveyor/ci/master/scripts/enable-desktop.ps1'))
         }
-  - if "%PLATFORM%" == "x64" set "URHO3D_64BIT=1"
+  - if "%PLATFORM%" == "x64" (
+      call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars64.bat" &&
+      set "URHO3D_64BIT=1"
+    ) else (
+      call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars32.bat"
+    )
   # rake ci_setup_cache
 build_script:
   - rake ci && if "%PACKAGE_UPLOAD%" == "1" (rake ci_package_upload && move %build_tree%\*.zip . && rd /S /Q %build_tree%\_CPack_Packages)

Rakefile

@@ -349,7 +349,7 @@ task :ci do
   # Currently we don't have the infra to test run all the platforms; also skip when doing packaging build due to time constraint
   ENV['URHO3D_TESTING'] = '1' if (((ENV['LINUX'] && !ENV['URHO3D_64BIT']) || (ENV['OSX'] && !ENV['IOS'] && !ENV['TVOS']) || ENV['APPVEYOR']) && !ENV['PACKAGE_UPLOAD']) || ENV['WEB']
   # When not explicitly specified then use generic generator
-  generator = ENV['XCODE'] ? 'xcode' : (ENV['APPVEYOR'] && !ENV['MINGW'] ? 'vs2015' : '')
+  generator = ENV['XCODE'] ? 'xcode' : (ENV['APPVEYOR'] && !ENV['MINGW'] ? 'vs2017' : '')
   # LuaJIT on MinGW build is not possible on Travis-CI with Ubuntu 14.04 LTS still as its GCC cross-compiler does not have native exception handling
   # LuaJIT on Web platform is not possible
   jit = (ENV['WIN32'] && ENV['TRAVIS']) || ENV['WEB'] ? '' : 'JIT=1 URHO3D_LUAJIT_AMALG='