Replace the avhttp library used by the github plugin with libcurl.

pcbnew/github/github_plugin.h

@@ -210,14 +210,14 @@ protected:
      * @param  aZipURL is where to put the zip file URL.
      * @return bool - true if @a aRepoULR was parseable, else false
      */
-    static bool repoURL_zipURL( const wxString& aRepoURL, std::string* aZipURL );
+    static bool repoURL_zipURL( const wxString& aRepoURL, std::string& aZipURL );
 
     /**
-     * Function remote_get_zip
+     * Function remoteGetZip
      * fetches a zip file image from a github repo synchronously.  The byte image
      * is received into the m_input_stream.
      */
-    void remote_get_zip( const wxString& aRepoURL ) throw( IO_ERROR );
+    void remoteGetZip( const wxString& aRepoURL ) throw( IO_ERROR );
 
     wxString    m_lib_path;     ///< from aLibraryPath, something like https://github.com/liftoff-sr/pretty_footprints
     std::string m_zip_image;    ///< byte image of the zip file in its entirety.