Add appveyor configuration file, including scheduled coverity build

.appveyor.yml

@@ -0,0 +1,52 @@
+version: '{build}'
+
+branches:
+  only:
+  - master
+
+image: Visual Studio 2015
+
+configuration:
+  - Development
+  - Release
+
+platform:
+  - Win32
+  - x64
+
+clone_depth: 1
+
+environment:
+  coverity_token:
+    secure: cvo7MHcff1Razyw9WcbJVBrEP8MkGIo7kvJ1RHYFIu0=
+  coverity_email:
+    secure: ndq7n9R6NhCV8mENhPAH4VTFNUeROGK/uFlqfUVwxAc=
+
+install:
+- ps: $env:PATH = 'C:\MinGW\bin;C:\MinGW\mingw32\bin;C:\MinGW\msys\1.0\bin;' + $env:PATH
+
+build:
+  project: renderdoc.sln
+  parallel: true
+  verbosity: minimal
+
+build_script:
+- ps: >-
+    if ( ($env:APPVEYOR_SCHEDULED_BUILD -eq "True" ) -and ($env:PLATFORM -eq "x64") -and ($env:CONFIGURATION -eq "Development") )
+    {
+      cov-build.exe --dir cov-int msbuild renderdoc.sln /p:Configuration=Development /p:Platform=x64 /p:PlatformToolset=v120
+
+      nuget.exe install PublishCoverity -ExcludeVersion
+      PublishCoverity\tools\PublishCoverity.exe compress -o coverity.zip -i cov-int
+      PublishCoverity\tools\PublishCoverity.exe publish `
+        -t "$env:coverity_token" `
+        -e "$env:coverity_email" `
+        -r "$env:APPVEYOR_REPO_NAME" `
+        -z coverity.zip `
+        -d "AppVeyor scheduled build ($env:APPVEYOR_REPO_COMMIT)." `
+        --codeVersion "$env:APPVEYOR_REPO_COMMIT"
+      return
+    }
+
+    sh -c ./hash_version.sh
+    msbuild renderdoc.sln "/p:Configuration=$env:CONFIGURATION" "/p:Platform=$env:PLATFORM" /p:PlatformToolset=v140