Armel Asselin separated CA cert verification problems from problems with

reading the (local) CA cert file to let users easier pinpoint the actual
problem. CURLE_SSL_CACERT_BADFILE (77) is the new libcurl error code.

include/curl/curl.h

@@ -390,6 +390,8 @@ typedef enum {
                                     CURLOPT_CONV_FROM_NETWORK_FUNCTION,
                                     CURLOPT_CONV_TO_NETWORK_FUNCTION, and
                                     CURLOPT_CONV_FROM_UTF8_FUNCTION */
+  CURLE_SSL_CACERT_BADFILE,      /* 77 - could not load CACERT file, missing
+                                    or wrong format */
   CURL_LAST /* never use! */
 } CURLcode;