pl_PL locale: Base collation on iso14651_t1

	[BZ #22469]
	* localedata/locales/pl_PL (LC_COLLATE): Use “copy "iso14651_t1"”
	and implement the collation rules for pl from CLDR on top of that.
	* Makefile: Add pl_PL.UTF-8 to test-input and to the list
	of locales to be built for testing.
	* pl_PL.UTF-8.in: New file with test data to test the Polish sorting.