Update submodule websocketpp to 0.8.2 (#1392)

* Update submodule websocketpp to 0.8.2

- Update to WebSocket++/0.8.2
  commit 56123c87598f8b1dd471be83ca841ceae07f95ba
- Fixes build issues with boost 1.70 and newer

* Update vcpkg.

* Remove defunct VS2015 configurations.

Co-authored-by: Billy Robert O'Neal III <[email protected]>

Author: c72578

Release/libs/websocketpp

@@ -21,16 +21,6 @@ jobs:
       name: 'Windows_VS2017_x64'
       targetPlatform: x64
       image: 'vs2017-win2016'
-  - template: azure-devops/build-windows.yml
-    parameters:
-      name: 'Windows_VS2015_x86'
-      targetPlatform: x86
-      image: 'vs2015-win2012r2'
-  - template: azure-devops/build-windows.yml
-    parameters:
-      name: 'Windows_VS2015_x64'
-      targetPlatform: x64
-      image: 'vs2015-win2012r2'
   - job: Windows_VS2019_UWP
     pool:
       vmImage: 'windows-latest'