examples: Include hello-*.pot in the distribution
Partially revert 2c3d71ce, as it broke "make dist". Instead,
include all the generated POT files in the distribution to prevent
re-generation of those files.
* Makefile.am (distdir1): Call update-po in po/Makefile.
* po/Makefile.am ($(DOMAIN).pot-update): Specify --directory for
xgettext invocation.
(DISTCLEANFILES): Move $(SMALLPOTS)...
(MAINTAINERCLEANFILES): ...here.
(distdir1): Include $(SMALLPOTS) in the distribution.
