Checking that curl_exec is available and if it isn't show an error message.

git-svn-id: https://plugins.svn.wordpress.org/wripl/trunk@798628 b8457f37-d9ea-0310-8a92-e5e31aec5664
version 1.5.1

git-svn-id: https://plugins.svn.wordpress.org/wripl/trunk@798630 b8457f37-d9ea-0310-8a92-e5e31aec5664