Put default initialisation of bv_encodingt in its definition

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

Author: thomasspriggs

src/util/bv_encoding.h

@@ -14,10 +14,8 @@ Author: Diffblue Ltd
 struct bv_encodingt final
 {
   // 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;
 };
 
 #endif // CPROVER_UTIL_BV_ENCODING_H

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;