* tests/Makefile.am (TESTS): Rearrange into other veriables, and
include run-markup-tests.sh.
(TESTS_ENVIRONMENT): New.  Pass $srcdir to tests.
(noinst_PROGRAMS): Rename to ...
(check_PROGRAMS): ... this.  'automake' ensures that these are
built before running the tests.
* tests/run-markup-tests.sh: Support $srcdir != $builddir.