Merge pull request #1861 from gennadiycivil/master

adding c++11 to appveyor mingW and autotools build

.travis.yml

@@ -26,6 +26,7 @@ matrix:
       compiler: gcc
       install: ./ci/install-linux.sh && ./ci/log-config.sh
       script: ./ci/build-linux-autotools.sh
+      env: VERBOSE=1 CXX_FLAGS=-std=c++11
     - os: linux
       group: deprecated-2017Q4
       compiler: gcc

appveyor.yml

@@ -23,6 +23,8 @@ environment:
     - compiler: gcc-5.3.0-posix
       generator: "MinGW Makefiles"
       cxx_path: 'C:\mingw-w64\i686-5.3.0-posix-dwarf-rt_v4-rev0\mingw32\bin'
+      cxx_options: "-std=gnu++11"
+      enabled_on_pr: yes
 
     - compiler: gcc-6.3.0-posix
       generator: "MinGW Makefiles"