Avoid duplicate lib flags in configuration for PolyML 5.5.1 (and above) under Darwin.

It is probably better to simplify things further, i.e. make sure users build PolyML using the option --enable-shared (which is no longer the default). In particular, -lgmp is problematic because not all users will build PolyML with GMP support enabled.
Self-test for important "non-idempotence" property of HOLsets.

In particular, if the set's comparison function is an equivalence
relation, then check that adding x0 and then x1 (where x0 \equiv x1),
results in a set containing x1, not x0.
Get new selftest (from db32edaf6) to actually compile.  (Sheesh)
Use sets instead of lists to keep Overload print_maps small.

Thanks to Scott to raising this issue. The use of a functor is so that
I can use the same code for Anthony's use of LVTermNet, but have the
underlying type be a list (this for the sake of backwards
compatibility).
Add more stuff to the Travis selftestseq
Remove examples/misc from Travis selftestseq.

It depends on src/real because of root2Theory.
removed -lgmp flag
Merge branch 'master' into add_satisfy_ss
Fix examples/lambda/basics/generic_termsScript with SATISFY_ss in srw_ss.