base: support module name override with std.base.export.

* lib/std/base/list.lua (compare): Move from here...
* lib/std/base.lua (compare): ...to here.
* lib/std/base/list.lua: Remove.
* local.mk (dist_luastdbase_DATA): Remove lib/std/base/list.lua.
* lib/std/list.lua (M.compare): Provide explicit module name
argument.
* lib/std/base.lua (export): If an explicit module name was
passed, use that instead of reverse engineering it from the
source file containing an exported function.

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