Add an implementation of TGTA minimization

* src/ta/taexplicit.cc, src/ta/taexplicit.hh: Bug fix TGTA
* src/taalgos/minimize.cc,src/taalgos/minimize.hh: TGTA minimization
* src/taalgos/tgba2ta.cc: add a TGTA minimization command (uses -Rm)
* src/taalgos/minimize.cc, src/taalgos/minimize.hh
(minimize_tgbta): New function.
* src/taalgos/tgba2ta.cc: Set livelock-accepting flag of TGTA states
to false so they can be merged with other states.
* src/ta/taexplicit.cc (hash): Use id.
* src/ta/taexplicit.hh: Cosmetics.

src/taalgos/minimize.hh

@@ -22,6 +22,7 @@
 # define SPOT_TAALGOS_MINIMIZE_HH
 
 # include "ta/ta.hh"
+# include "ta/tgbta.hh"
 # include "ta/taexplicit.hh"
 
 namespace spot
@@ -30,6 +31,9 @@ namespace spot
   ta*
   minimize_ta(const ta* ta_);
 
+  tgbta*
+  minimize_tgbta(const tgbta* tgbta_);
+
 
 /// @}
 }