gnu: commoncpp: Add support for gnu updater.

* gnu/packages/telephony.scm (commoncpp)[properties]: New field. Add
ftp-directory, upstream-name.

gnu/packages/telephony.scm

@@ -209,6 +209,8 @@ (define-public commoncpp
 serialization and XML parsing.  It includes the uCommon C++ library, a smaller
 reimplementation.")
    (license license:gpl2+) ; plus runtime exception
+   (properties '((ftp-directory . "/gnu/commoncpp")
+                 (upstream-name . "commoncpp2")))
    (home-page "https://www.gnu.org/software/commoncpp/")))
 
 (define-public ucommon