Fix base type for nested types with enum or atom2 sub-types

To determine the base type structs and packed arrays call the
figure_packed_base_type() for their sub-types.

This method is not defined for enum or atom2 types and the default
implementation returns IVL_VT_NO_TYPE.

As a result packed arrays of enum or atom2 types and packed structs with
members of enum or atom2 types get elaborated with IVL_VT_NO_TYPE
as the base type.

For example

```
struct packed {
  bit signed [31:0] x;
} s1;
```

gets elaborated with a base type of IVL_VT_BOOL, while

```
struct packed {
  int x;
} s2;
```

gets elaborated with a base type of IVL_VT_NONE.

To fix this define the figure_packed_base_type() for enum_type_t and
atom2_type_t.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>

pform_types.cc

@@ -48,6 +48,16 @@ ivl_variable_type_t vector_type_t::figure_packed_base_type(void) const
       return base_type;
 }
 
+ivl_variable_type_t enum_type_t::figure_packed_base_type() const
+{
+      return base_type;
+}
+
+ivl_variable_type_t atom2_type_t::figure_packed_base_type() const
+{
+      return IVL_VT_BOOL;
+}
+
 atom2_type_t size_type (32, true);
 
 PNamedItem::SymbolType enum_type_t::symbol_type() const

pform_types.h

@@ -182,6 +182,8 @@ struct enum_type_t : public data_type_t {
 	// Return the elaborated version of the type.
       virtual ivl_type_s*elaborate_type_raw(Design*des, NetScope*scope) const;
 
+      ivl_variable_type_t figure_packed_base_type() const;
+
       SymbolType symbol_type() const;
 
       ivl_variable_type_t base_type;
@@ -217,6 +219,8 @@ struct atom2_type_t : public data_type_t {
       virtual std::ostream& debug_dump(std::ostream&out) const;
 
       ivl_type_s* elaborate_type_raw(Design*des, NetScope*scope) const;
+
+      ivl_variable_type_t figure_packed_base_type() const;
 };
 
 extern atom2_type_t size_type;