Fix logic choice for CVC4

CVC4 allows ALL logic to be specified which in turn allows for
quantifiers in forumulas.

Fixes diffblue#5977

Author: TGWDB

src/solvers/smt2/smt2_conv.cpp

@@ -96,6 +96,7 @@ smt2_convt::smt2_convt(
     break;
 
   case solvert::CVC4:
+    logic = "ALL";
     use_array_of_bool = true;
     use_as_const = true;
     break;