configury: correctly install formatters to formatter subdir.

* local.mk (luaspecldir, dist_luaspecl_DATA): Rename from these...
(specldir, dist_specl_DATA): ...to these.
(formatterdir): New macro.  Formatter subdirectory.
(dist_specl_DATA): Move formatter/progress.lua,
formatter/report.lua and formatter/tap.lua from here...
(dist_formatter_DATA): ...to here.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>