fix m4/libcurl.m4 error when using libcurl without curl-config
fix m4/libcurl.m4 error when using libcurl without curl-config
pmq20/libmicrohttpd,slackner/libmicrohttpd,pmq20/libmicrohttpd,pmq20/libmicrohttpd,slackner/libmicrohttpd,slackner/libmicrohttpd