buddy: rename libbdd to libbddx

* buddy/src/bdd.h, buddy/src/bvec.h, buddy/src/fdd.h: Rename as...
* buddy/src/bddx.h, buddy/src/bvecx.h, buddy/src/fddx.h: ... these.
* buddy/src/Makefile.am: Build libbddx.la instead of libbdd.la.
* buddy/examples/Makefile.def: Use it.
* Makefile.am, buddy/src/bddtest.cxx, buddy/src/bvec.c,
buddy/src/cppext.cxx, buddy/src/fdd.c, buddy/src/imatrix.h,
buddy/src/kernel.h, buddy/examples/adder/adder.cxx,
buddy/examples/bddcalc/parser_.h, buddy/examples/bddtest/bddtest.cxx,
buddy/examples/cmilner/cmilner.c, buddy/examples/fdd/fdd.cxx,
buddy/examples/milner/milner.cxx, buddy/examples/money/money.cxx,
buddy/examples/queen/queen.cxx, buddy/examples/solitare/solitare.cxx,
m4/buddy.m4, src/ltlvisit/apcollect.hh, src/ltlvisit/simplify.hh,
src/misc/bddlt.hh, src/misc/bddop.hh, src/misc/minato.hh,
src/priv/acccompl.hh, src/priv/accconv.hh, src/priv/accmap.hh,
src/priv/bddalloc.cc, src/tgba/bdddict.hh, src/tgba/bddprint.hh,
src/tgba/tgbamask.hh, src/tgba/tgbasafracomplement.cc,
src/tgbaalgos/emptiness.hh, src/tgbaalgos/gtec/sccstack.hh,
src/tgbaalgos/neverclaim.cc, src/tgbaalgos/powerset.cc,
src/tgbaalgos/sccfilter.hh, src/tgbaalgos/sccinfo.hh,
src/tgbaalgos/weight.hh, wrap/python/buddy.i: Adjust.
* NEWS, README: Document it.

NEWS

@@ -2,6 +2,10 @@ New in spot 1.99a (not yet released)
 
   * Major changes (including backward incompatible changes):
 
+    - The curstomized version of BuDDy (libbdd) used by Spot has be
+      renamed as (libbddx) to avoid issues with copies of BuDDy
+      already installed on the system.
+
     - ltlgrind is a new tool that mutates LTL or PSL formulas.  If you
       have a tool that is bogus on some formula that is tool large to
       debug, you can use ltlgrind to generate smaller derived formulas