(Ara) Replace two 2-valued params in VP with one 3-valued param.

* is copula / is have_V2 / is neither

There is no difference; all three options are is mutually exclusive. 
There 2 params in the first place only by accident. First one was added 
by AED 10 years agon, second by me only some weeks ago, without thinking 
that the params are mutually exclusive.

Also tested with gftest, no difference found after 2 hours of running.

src/arabic/VerbAra.gf

@@ -16,7 +16,7 @@ concrete VerbAra of Verb = CatAra ** open Prelude, ResAra, ParamX in {
                        ++ vp.s ! pgn ! VPImpf Cnj -- this will agree with the object added by ComplSlash
                        ++ vp.obj.s ;
         obj = emptyObj ;
-        isPred = False ;
+        vtype = NotPred ;
         c2 = v2v.c2 ; -- preposition for the direct object
         sc = v2v.sc
       } ;
@@ -30,7 +30,7 @@ concrete VerbAra of Verb = CatAra ** open Prelude, ResAra, ParamX in {
                       ++ vps.s ! np.a.pgn ! VPImpf Cnj -- verb from old VP agrees with object
                       ++ vps.obj.s ; -- otherwise obj appears in a weird place /IL
         obj = emptyObj ;
-        isPred = False ;
+        vtype = NotPred ;
                     -- preposition for the direct object comes from VP
         sc = v2v.sc
       } ;
@@ -68,7 +68,7 @@ concrete VerbAra of Verb = CatAra ** open Prelude, ResAra, ParamX in {
         s = \\pgn,vpf => vvVP.s ! pgn ! vpf
                       ++ vv.s2  -- أَنْ
                       ++ vp.s ! pgn ! VPImpf Cnj ;
-        isPred = False ;
+        vtype = NotPred ;
         sc = vv.sc
       } ;
 
@@ -92,7 +92,7 @@ concrete VerbAra of Verb = CatAra ** open Prelude, ResAra, ParamX in {
     UseComp xabar =
       case xabar.isNP of {
         False => kaan xabar ;
-        True  => predV copula ** {obj = xabar.obj ; isPred=True}
+        True  => predV copula ** {obj = xabar.obj ; vtype=Copula}
       } ;
 
     UseCopula = predV copula ;