* gnu/packages/base.scm (make-glibc-locales, make-glibc-utf8-locales): New
procedures.
(glibc-locales): Express in terms of make-glibc-locales.
(glibc-utf8-locales): Express in terms of make-glibc-utf8-locales.
(glibc-locales-2.27, glibc-utf8-locales-2.27): New variables.