Encode integer addresses together with pointer object/offset

Instead of encoding pointers with the same bit width a pointer on a
given platform has, just widen the bit-blasted encoding to include both
the previous object/offset encoding as well as an (integer) address. The
encoding is thus also trivially extended to handle larger numbers of
objects and offsets of the same width as the address.

Furthermore clean up the code to encapsulate encoding properly, and make
in-code layout of pointer encoding more natural (it's now object,
offset, integer-address).

Fixes: #436
Fixes: #311
Fixes: #94

Author: tautschnig

regression/cbmc/Pointer_Arithmetic12/test.desc

@@ -1,8 +1,10 @@
-CORE
+THOROUGH
 main.i
 --32 --little-endian
 ^EXIT=0$
 ^SIGNAL=0$
 ^VERIFICATION SUCCESSFUL$
 --
 ^warning: ignoring
+--
+Takes around 2 minutes to run.

regression/cbmc/Pointer_Arithmetic13/test.desc

@@ -1,4 +1,4 @@
-KNOWNBUG
+CORE
 main.c
 
 ^EXIT=0$

regression/cbmc/Pointer_Arithmetic18/test.desc

@@ -1,4 +1,4 @@
-KNOWNBUG
+CORE
 main.c
 --32
 ^EXIT=0$

regression/cbmc/Pointer_comparison1/test.desc

@@ -1,4 +1,4 @@
-KNOWNBUG
+CORE
 main.c
 
 ^EXIT=10$

regression/cbmc/address_space_size_limit1/test.c

@@ -1,4 +1,4 @@
-CORE
+THOROUGH
 main.i
 --32 --little-endian --object-bits 25 --pointer-check
 ^EXIT=10$

regression/cbmc/address_space_size_limit1/test.desc

@@ -27,15 +27,12 @@ boolbv_widtht::~boolbv_widtht()
 
 std::size_t boolbv_widtht::get_object_width(const pointer_typet &type) const
 {
-  return config.bv_encoding.object_bits;
+  return type.get_width();
 }
 
 std::size_t boolbv_widtht::get_offset_width(const pointer_typet &type) const
 {
-  const std::size_t pointer_width = type.get_width();
-  const std::size_t object_width = get_object_width(type);
-  PRECONDITION(pointer_width >= object_width);
-  return pointer_width - object_width;
+  return type.get_width();
 }
 
 std::size_t boolbv_widtht::get_address_width(const pointer_typet &type) const
@@ -203,8 +200,9 @@ const boolbv_widtht::entryt &boolbv_widtht::get_entry(const typet &type) const
   }
   else if(type_id==ID_pointer)
   {
+    const pointer_typet &t = type_checked_cast<pointer_typet>(type);
     entry.total_width =
-      get_address_width(type_checked_cast<pointer_typet>(type));
+      get_address_width(t) + get_object_width(t) + get_offset_width(t);
     DATA_INVARIANT(entry.total_width != 0, "pointer must have width");
   }
   else if(type_id==ID_struct_tag)