Adding tools now missing in appveyor (etr#252)

Author: etr

appveyor.yml

@@ -16,6 +16,7 @@ init:
   - ps: iex ((new-object net.webclient).DownloadString('https://raw.githubusercontent.com/appveyor/ci/master/scripts/enable-rdp.ps1'))
 install:
   - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -msys2 -c "pacman --noconfirm -S --needed mingw-w64-$MSYS2_ARCH-{libtool,make,pkg-config,libsystre,doxygen,gnutls,graphviz,curl}"'
+  - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -msys2 -c "pacman --noconfirm -S --needed autotools"'
   - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && curl https://s3.amazonaws.com/libhttpserver/libmicrohttpd_releases/libmicrohttpd-0.9.59.tar.gz -o libmicrohttpd-0.9.59.tar.gz"'
   - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER && tar -xzf libmicrohttpd-0.9.59.tar.gz"'
   - 'if "%compiler%"=="msys2" C:\msys64\msys2_shell.cmd -defterm -no-start -mingw64 -full-path -here -c "cd $APPVEYOR_BUILD_FOLDER/libmicrohttpd-0.9.59 && ./configure --disable-examples --enable-poll=no --prefix /C/msys64 && make && make install"'