Added back full appveyor test matrix

.appveyor.yml

@@ -9,9 +9,29 @@ configuration:
   - Release
 
 image:
+  - Visual Studio 2013
   - Visual Studio 2015
   - Visual Studio 2017
 
+environment:
+  matrix:
+    - GLM_ARGUMENTS: -DGLM_TEST_FORCE_PURE=ON
+    - GLM_ARGUMENTS: -DGLM_TEST_ENABLE_SIMD_SSE2=ON -DGLM_TEST_ENABLE_LANG_EXTENSIONS=ON
+    - GLM_ARGUMENTS: -DGLM_TEST_ENABLE_SIMD_AVX=ON -DGLM_TEST_ENABLE_LANG_EXTENSIONS=ON
+
+matrix:
+    exclude:
+    - image: Visual Studio 2013
+      GLM_ARGUMENTS: -DGLM_TEST_ENABLE_SIMD_AVX=ON -DGLM_TEST_ENABLE_LANG_EXTENSIONS=ON
+    - image: Visual Studio 2013
+      configuration: Debug
+    - image: Visual Studio 2015
+      platform: x86
+    - image: Visual Studio 2015
+      configuration: Debug
+    - image: Visual Studio 2017
+      platform: x86
+
 cache:
   - C:\cmake-3.8.0-win32-x86
 
@@ -28,16 +48,20 @@ before_build:
       mkdir build
       cd build
 
+      if ("$env:APPVEYOR_JOB_NAME" -match "Image: Visual Studio 2013") {
+          $env:generator="Visual Studio 12 2013"
+      } 
       if ("$env:APPVEYOR_JOB_NAME" -match "Image: Visual Studio 2015") {
           $env:generator="Visual Studio 14 2015"
-      } else {
+      } 
+      if ("$env:APPVEYOR_JOB_NAME" -match "Image: Visual Studio 2017") {
           $env:generator="Visual Studio 15 2017"
       }
       if ($env:PLATFORM -eq "x64") {
           $env:generator="$env:generator Win64"
       }
       echo generator="$env:generator"
-      cmake .. -G "$env:generator" -DGLM_QUIET=ON -DGLM_TEST_ENABLE=ON
+      cmake .. -G "$env:generator" -DGLM_QUIET=ON -DGLM_TEST_ENABLE=ON "$env:GLM_ARGUMENTS"
 
 build_script:
   - cmake --build . --config %CONFIGURATION% -- /m /v:minimal