AppVeyor: updated to handle OpenSSL/WinSSL builds

Closes #621

appveyor.yml

@@ -1,19 +1,35 @@
-version: 7.45.0.{build}
+version: 7.47.0.{build}
 
 environment:
     matrix:
       - PRJ_GEN: "Visual Studio 11 2012 Win64"
         BDIR: msvc2012
         PRJ_CFG: Release
+        OPENSSL: OFF
       - PRJ_GEN: "Visual Studio 12 2013 Win64"
         BDIR: msvc2013
         PRJ_CFG: Release
+        OPENSSL: OFF
       - PRJ_GEN: "Visual Studio 14 2015 Win64"
         BDIR: msvc2015
         PRJ_CFG: Release
+        OPENSSL: OFF
+      - PRJ_GEN: "Visual Studio 11 2012 Win64"
+        BDIR: msvc2012
+        PRJ_CFG: Release
+        OPENSSL: ON
+      - PRJ_GEN: "Visual Studio 12 2013 Win64"
+        BDIR: msvc2013
+        PRJ_CFG: Release
+        OPENSSL: ON
+      - PRJ_GEN: "Visual Studio 14 2015 Win64"
+        BDIR: msvc2015
+        PRJ_CFG: Release
+        OPENSSL: ON
+
 
 build_script:
     - mkdir build.%BDIR%
     - cd build.%BDIR%
-    - cmake .. -G"%PRJ_GEN%"
+    - cmake .. -G"%PRJ_GEN%" -DCMAKE_USE_OPENSSL=%OPENSSL%
     - cmake --build . --config %PRJ_CFG% --clean-first