Improve gen-locales.mk and gen-locale.sh to make test files with @ options work

With out this, adding collation test files like localedata/gez_ER.UTF-8@abegede.in
does not work for locales which contain @ modifiers.

	* gen-locales.mk: Make test files which contain @ modifiers in their
        name work.
	* localedata/gen-locale.sh: Likewise.