For AppVeyor - redirect some of the output stream to null device.

Skip *.chm generation on AppVeyor due to a similar issue reported in #910.
Test [ci package] on [ci only: AppVeyor].

.appveyor.yml

@@ -39,16 +39,15 @@ install:
         {
           if ($env:APPVEYOR_REPO_TAG -eq "false")
           {
-            git fetch --unshallow;
             $env:UPLOAD_DIR = "/home/frs/project/$env:APPVEYOR_PROJECT_SLUG/Snapshots";
+            git fetch -q --unshallow;
           }
           else
           {
             $env:UPLOAD_DIR = "/home/frs/project/$env:APPVEYOR_PROJECT_SLUG/$env:APPVEYOR_REPO_TAG_NAME";
           }
           $env:PACKAGE_UPLOAD = '1';
-          choco install doxygen.portable;
-          choco install graphviz.portable;
+          choco install doxygen.portable graphviz.portable >$null;
         }
 build_script:
   - if "%PLATFORM%" == "x64" set "OPTS=URHO3D_64BIT=1"
@@ -56,7 +55,8 @@ build_script:
   - rake make config=%CONFIGURATION%
 # Could run test target as AppVeyor does not have service similar to xvfb for headless GUI test run
 # - rake make config=%CONFIGURATION% target=RUN_TESTS
-  - if "%PACKAGE_UPLOAD%" == "1" rake make config=%CONFIGURATION% target=doc && rake make config=%CONFIGURATION% target=package
+  - if "%PACKAGE_UPLOAD%" == "1" (rake make config=%CONFIGURATION% target=doc
+                                  rake make config=%CONFIGURATION% target=package)
 test: off
 artifacts:
   - path: ..\native-Build\*.zip

Docs/CMakeLists.txt

@@ -66,7 +66,7 @@ if (DOXYGEN_FOUND)
         foreach (IDE XCODE MSVC Eclipse CodeBlocks)
             enable_help (${IDE})
         endforeach ()
-        if (MSVC_HELP)
+        if (MSVC_HELP AND NOT DEFINED ENV{APPVEYOR})    # Skip when generating MSVC help on AppVeyor due to similar issue to #910
             find_package (HTMLHelp)
             # It is not an error when HTML help compiler is not found, instead just switching off the Doxygen's HHC option
             find_package_handle_standard_args (HTMLHelp REQUIRED_VARS HTML_HELP_COMPILER)