Merge branch 'js/no-curl-easy-strerror-on-old-curl'

Merge branch 'js/no-curl-easy-strerror-on-old-curl'

Done to support compilation on __TANDEM, but is independently useful
for people with older version of libcURL.

* js/no-curl-easy-strerror-on-old-curl:
  http.c: don't use curl_easy_strerror prior to curl-7.12.0