Use -fvisibility=hidden in src/tgbaalgos/.

* src/tgbaalgos/Makefile.am, src/tgbaalgos/gtec/Makefile.am: Add
$(VISIBILITY_CXXFLAGS).
* src/tgbaalgos/bfssteps.hh, src/tgbaalgos/compsusp.hh,
src/tgbaalgos/cutscc.hh, src/tgbaalgos/cycles.hh,
src/tgbaalgos/degen.hh, src/tgbaalgos/dotty.hh,
src/tgbaalgos/dottydec.hh, src/tgbaalgos/dupexp.hh,
src/tgbaalgos/eltl2tgba_lacim.hh, src/tgbaalgos/emptiness.hh,
src/tgbaalgos/gtec/ce.hh, src/tgbaalgos/gtec/explscc.hh,
src/tgbaalgos/gtec/gtec.hh, src/tgbaalgos/gtec/nsheap.hh,
src/tgbaalgos/gtec/sccstack.hh,
src/tgbaalgos/gtec/status.hh, src/tgbaalgos/gv04.hh,
src/tgbaalgos/isdet.hh, src/tgbaalgos/isweakscc.cc,
src/tgbaalgos/isweakscc.hh, src/tgbaalgos/lbtt.hh,
src/tgbaalgos/ltl2taa.hh, src/tgbaalgos/ltl2tgba_fm.hh,
src/tgbaalgos/ltl2tgba_lacim.hh, src/tgbaalgos/magic.hh,
src/tgbaalgos/minimize.hh, src/tgbaalgos/neverclaim.hh,
src/tgbaalgos/postproc.hh, src/tgbaalgos/powerset.hh,
src/tgbaalgos/projrun.hh, src/tgbaalgos/randomgraph.hh,
src/tgbaalgos/reachiter.hh, src/tgbaalgos/reducerun.hh,
src/tgbaalgos/reductgba_sim.cc, src/tgbaalgos/reductgba_sim.hh,
src/tgbaalgos/replayrun.hh, src/tgbaalgos/rundotdec.hh,
src/tgbaalgos/safety.hh, src/tgbaalgos/save.hh, src/tgbaalgos/scc.hh,
src/tgbaalgos/sccfilter.hh, src/tgbaalgos/se05.hh,
src/tgbaalgos/simulation.hh, src/tgbaalgos/stats.hh,
src/tgbaalgos/stripacc.hh, src/tgbaalgos/tau03.hh,
src/tgbaalgos/tau03opt.hh, src/tgbaalgos/translate.hh: Mark public
symbol with SPOT_API.

src/tgbaalgos/postproc.hh

@@ -56,7 +56,7 @@ namespace spot
   /// when minimized_obligation failed to produce an automaton smaller
   /// than its input.  pref=Small,level=Low will only run
   /// simulation().
-  class postprocessor
+  class SPOT_API postprocessor
   {
   public:
     /// \brief Construct a postprocessor.