Merge branch 'pull/collectd-4.1' into collectd-4.1

diff --cc configure.in
index a13b79c,51f26c3..54d38d5
--- 1/configure.in
--- 2/configure.in
+++ b/configure.in
@@@ -770,14 -770,15 +770,16 @@@ AC_ARG_WITH(libcurl, [AS_HELP_STRING([-
        then
                with_libcurl="yes"
        else
 -              if test -x "$withval"
 +              if test -f "$withval" && test -x "$withval"
                then
                        with_curl_config="$withval"
+                       with_libcurl="yes"
                else if test -x "$withval/bin/curl-config"
                then
                        with_curl_config="$withval/bin/curl-config"
+                       with_libcurl="yes"
                fi; fi
 +              with_libcurl="yes"
        fi; fi
  ],
  [