argument to Guile's `member' and `assoc' functions has a different expected
arity.
* module/rnrs/lists.scm (memp, assp): Wrap the predicate function with a
two-argument wrapper before calling Guile's underlying implemenation.
* test-suite/Makefile.am: Add test-suite/tests/r6rs-lists.test to
SCM_TESTS.
* test-suite/tests/r6rs-lists.test: New file.