AppVeyor: add configuration file

.appveyor.yml

@@ -0,0 +1,18 @@
+version: '{build}'
+
+image: Visual Studio 2015
+
+pull_requests:
+  do_not_increment_build_number: true
+
+skip_branch_with_pr: true
+
+clone_depth: 1
+
+init:
+- ps: Update-AppveyorBuild -Version "build-$env:appveyor_build_number-$($env:appveyor_repo_commit.substring(0,7))"
+
+build_script:
+- cmd: >-
+    src\BuildAll.cmd
+    exit %errorlevel%