1) compute path to i386 compiler from configure.  If it is found, run
the i386 tests.  I use macros so that this approach could be applied
for other arches as well.

2) provide an easily extensible way to add tests

Most tests fail, but at least "make test" does something meaningful.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>