Fix ATF-Kit on Tiger Intel.
        * taf-kit/src/Makefile.am (vcsn_b_LDADD): Rename as...
        (LDADD): these, since they all need argp.
        Pass CONTEXT only, not CONTEXT_HEADER and CONTEXT_NAMESPACE.
        * taf-kit/src/common.hh: Adjust to define them.

        * build-aux/check.mk (check-TESTS): Don't rely on wc not outputing
        space when used as a filter, since that's not what Tiger's wc
        does.  Use grep -c.