url: use the URL API internally as well

... to make it a truly unified URL parser.

Closes #3017

lib/ftp.h

@@ -105,6 +105,8 @@ struct FTP {
   curl_off_t *bytecountp;
   char *user;    /* user name string */
   char *passwd;  /* password string */
+  char *path;    /* points to the urlpieces struct field */
+  char *pathalloc; /* if non-NULL a pointer to an allocated path */
 
   /* transfer a file/body or not, done as a typedefed enum just to make
      debuggers display the full symbol and not just the numerical value */