add axllib tests to make check

some are broken, they should be fixed and added, as well
use peter's workaround for if4 test
fix dependencies for parallel build of test programs
enable now-working tests
don't use SUBDIRS for test programs
move Tests.am generation code out into testprog.am
correct XFAIL_TESTS for axldem
test_tinfer: Add checks for mutually referential types and value
conditionals (taken from if4.as)
Merge branch 'axllib-tests' into pab/tmp/testmerge
The form A: BT == add { local AAA: BT with == add; ...}
ie. nested adds with a category in both inner and outer adds was not
quite working - the "%%: BT" symbol was not present in the inner add,
and so picked up from the outer.. so you get a big kaboomy noise.

This also shows in bug1253 - outer definitions being picked up by 'add'.