gnu: liblinphone: Fix the input type of some dependencies.

Libraries being linked to such as libxml2, libiconv and zlib should appear as
'inputs' rather than 'native-inputs'.

* gnu/packages/linphone.scm (liblinphone)[native-inputs]: Move libiconv,
libxml2 and zlib to...
[inputs]: ...here.  Move eudev, python-pystache and python-six to
native-inputs.

gnu/packages/linphone.scm

@@ -447,27 +447,28 @@ (define-public liblinphone
                 ""))
              #t)))))
     (native-inputs
-     `(("dot" ,graphviz)
+     `(("gettext" ,gettext-minimal)
+       ("udev" ,eudev)                  ;for libudev.h
+       ;; For generating the C++ wrappers.
+       ("dot" ,graphviz)
        ("doxygen" ,doxygen)
-       ("gettext" ,gettext-minimal)
-       ("iconv" ,libiconv)
        ("python" ,python)
-       ("xml2" ,libxml2)
-       ("zlib" ,zlib)))
+       ("pystache" ,python-pystache)
+       ("six" ,python-six)))
     (inputs
      `(("bctoolbox" ,bctoolbox)
        ("belcard" ,belcard)
        ("bellesip" ,belle-sip)
        ("bzrtp", bzrtp)
+       ("iconv" ,libiconv)
        ("glib" ,glib)
        ("gtk2" ,gtk+-2)
        ("mediastreamer2" ,mediastreamer2)
        ("notify" ,libnotify)
        ("ortp" ,ortp)
-       ("pystache" ,python-pystache)
-       ("six" ,python-six)
        ("sqlite" ,sqlite)
-       ("udev" ,eudev)))
+       ("xml2" ,libxml2)
+       ("zlib" ,zlib)))
     (synopsis "Belledonne Communications Softphone Library")
     (description "Liblinphone is a high-level SIP library integrating
 all calling and instant messaging features into an unified