Updating Translation Makefile for Newer Sphin-intl

[xie-dongping]

In the newer version (0.9.7 and on) of sphinx-intl, the build command must be combined with a -l switch.

So the Makefile should be fix to be able to compile the Chinese version.

[xogeny]

Maybe @dietmarw can confirm this is working as part of #326.

[dietmarw]

@xie-dongping I think this should work as it is now. But better have another look.