Add new constructors for ast_type_specifier

Add a constructor that uses an ast_struct_specifier and one that uses
a type name.  This saves a (trivial) bit of code, but it also ensures
some of the class invariants (i.e., type_name != NULL) are met.

ast.h

@@ -357,6 +357,22 @@ class ast_type_specifier : public ast_node {
 public:
    ast_type_specifier(int specifier);
 
+   /** Construct a type specifier from a type name */
+   ast_type_specifier(const char *name) 
+      : type_specifier(ast_type_name), type_name(name), structure(NULL),
+	is_array(false), array_size(NULL), precision(ast_precision_high)
+   {
+      /* empty */
+   }
+
+   /** Construct a type specifier from a structure definition */
+   ast_type_specifier(ast_struct_specifier *s)
+      : type_specifier(ast_struct), type_name(s->name), structure(s),
+	is_array(false), array_size(NULL), precision(ast_precision_high)
+   {
+      /* empty */
+   }
+
    virtual void print(void) const;
 
    enum ast_types type_specifier;

glsl_parser.ypp

@@ -861,13 +861,11 @@ type_specifier_nonarray:
 	}
 	| struct_specifier
 	{
-	   $$ = new ast_type_specifier(ast_struct);
-	   $$->structure = $1;
+	   $$ = new ast_type_specifier($1);
 	}
 	| TYPE_NAME
 	{
-	   $$ = new ast_type_specifier(ast_type_name);
-	   $$->type_name = $1;
+	   $$ = new ast_type_specifier($1);
 	}
 	;