[AppVeyor] Build curl in appveyor.

appveyor.yml

@@ -38,6 +38,7 @@ install:
 build_script:
   - appveyor\install_zlib.cmd
   - appveyor\install_lzma.cmd
+  - appveyor\install_libcurl.cmd
   - appveyor\install_pthread.cmd
   - appveyor\install_dirent.cmd
   - appveyor\install_xapian.cmd

appveyor/install_libcurl.cmd

@@ -0,0 +1,14 @@
+REM ========================================================
+REM Install libcurl
+curl -fsSL -O https://curl.haxx.se/download/curl-7.61.1.zip || exit /b 1
+7z x curl-7.61.1.zip || exit /b 1
+cd curl-7.61.1\winbuild
+nmake /f Makefile.vc mode=static MACHINE=x64 DEBUG=no VC=15 ENABLE_IDN=no || exit /b 1
+mkdir %EXTRA_DIR%\include\curl
+copy ..\builds\libcurl-vc15-x64-release-static-ipv6-sspi-winssl\include\curl\*.h %EXTRA_DIR%\include\curl
+copy ..\builds\libcurl-vc15-x64-release-static-ipv6-sspi-winssl\lib\libcurl_a.lib %EXTRA_DIR%\lib
+move %EXTRA_DIR%\lib\libcurl_a.lib %EXTRA_DIR%\lib\libcurl.a
+dir %EXTRA_DIR%\include\curl
+dir %EXTRA_DIR%\lib
+curl -fsSl -o%PKG_CONFIG_PATH%\libcurl.pc http://public.kymeria.fr/KIWIX/windows/libcurl.pc || exit /b 1
+cd ..\..