tests: migrate legacy tests/demo tests to Autotest.

tests: migrate legacy tests/demo tests to Autotest.

* tests/demo.at: New autotest groups, based on...
* tests/demo-conf.test, tests/demo-deplibs.test,
tests/demo-exec.test, tests/demo-hardcode.test,
tests/demo-inst.test, tests/demo-make.test,
tests/demo-nofast-exec.test, tests/demo-nofast-inst.test,
tests/demo-nofast-make.test, tests/demo-nofast-unst.test,
tests/demo-nofast.test, tests/demo-noinst-link.test,
tests/demo-nopic-exec.test, tests/demo-nopic-make.test,
tests/demo-nopic.test, tests/demo-pic-exec.test,
tests/demo-pic-make.test, tests/demo-pic.test,
tests/demo-relink.test, tests/demo-shared-exec.test,
tests/demo-shared-inst.test, tests/demo-shared-make.test,
tests/demo-shared-unst.test, tests/demo-shared.test,
tests/demo-static-exec.test, tests/demo-static-inst.test,
tests/demo-static-make.test, tests/demo-static-unst.test,
tests/demo-static.test, tests/demo-unst.test: ...these legacy
test cases, now removed.
* tests/demo/Makefile.am, tests/demo/README,
tests/demo/configure.ac, tests/demo/dlmain.c, tests/demo/foo.c,
tests/demo/foo.h, tests/demo/hell1.c, tests/demo/hell2.c,
tests/demo/hello.c, tests/demo/main.c: Remove.
* configure.ac (CONF_SUBDIRS): Remove tests/demo.
* Makefile.am: Adjust.

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