cashew: libcurl http fetcher: use default CA certificate path

src/libcurl_http_fetcher.h

Index: src/libcurl_http_fetcher.h
diff --git a/src/libcurl_http_fetcher.h b/src/libcurl_http_fetcher.h
index 93bd253635a25cfc5cd9332692c6e04ce325e667..7d066823a8751d638ee868bd7645a1e39d2bad3d 100644
--- a/src/libcurl_http_fetcher.h
+++ b/src/libcurl_http_fetcher.h
@@ -67,6 +67,9 @@ class LibcurlHttpFetcher : public HttpFetcher {
   void set_retry_seconds(int seconds) { retry_seconds_ = seconds; }
 
  private:
+  // Asks libcurl for the http response code and stores it in the object.
+  void GetHttpResponseCode();
+
   // Resumes a transfer where it left off. This will use the
   // HTTP Range: header to make a new connection from where the last
   // left off.