Put default initialisation of bv_encodingt in its definition

So that `bv_encodingt` can be more used without the need to explicitly
initialise its members.

Author: thomasspriggs

src/util/config.cpp

@@ -771,10 +771,6 @@ bool configt::set(const cmdlinet &cmdline)
 
   cpp.cpp_standard=cppt::default_cpp_standard();
 
-  bv_encoding.object_bits=bv_encoding.default_object_bits;
-  // This will allow us to override by language defaults later.
-  bv_encoding.is_object_bits_default=true;
-
   ansi_c.single_precision_constant=false;
   ansi_c.for_has_scope=true; // C99 or later
   ansi_c.ts_18661_3_Floatn_types=false;

src/util/config.h

@@ -173,10 +173,8 @@ class configt
   struct bv_encodingt
   {
     // number of bits to encode heap object addresses
-    std::size_t object_bits;
-    bool is_object_bits_default;
-
-    static const std::size_t default_object_bits=8;
+    std::size_t object_bits = 8;
+    bool is_object_bits_default = true;
   } bv_encoding;
 
   // this is the function to start executing