Fix po/Makefile.in.in being overwritten

As stated in the [intltool docs][1] `AM_GNU_GETTEXT*` macros should not be used in combination with `IT_PROG_INTLTOOL`. Otherwise autopoint will overwrite po/Makefile.in.in.

After applying this fix, the builds of `ppa:alexmurray/indicator-sensors-daily` for Trusty should work again and the package might be released for Trusty (some people seem to be interested e.g. [here][2] or [here][3])

[1]: https://code.launchpad.net/~robert-ancell/intltool/remove-am-gnu-gettext/+merge/114274
[2]: http://askubuntu.com/questions/450883/sensor-indicator-for-ubuntu-14-04
[3]: http://askubuntu.com/questions/449898/cpu-temperature-monitor-for-14-04lts