specs: copy symbols from `require "foo"` into local env.
specs: copy symbols from `require "foo"` into local env.

* src/specl.lua (initenv.require): Support consistent use of
`require "foo"` to import foo's global symbols into the local
environment, even when foo uses modern `return API_table` style.

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

gvvaughan/specl