[qfcc} Mark some more functions as pure

I guess gcc doesn't consider recursive functions as pure, but marking
get_type as pure had a slight ripple effect.

tools/qfcc/include/expr.h

@@ -263,7 +263,7 @@ extern expr_t *local_expr;
 	\return         Pointer to the type description, or null if the expression
 					type (expr_t::type) is inappropriate.
 */
-struct type_s *get_type (expr_t *e);
+struct type_s *get_type (expr_t *e) __attribute__((pure));
 
 /**	Get the basic type code of the expression result.
 
@@ -271,7 +271,7 @@ struct type_s *get_type (expr_t *e);
 	\return         Pointer to the type description, or ev_type_count if
 					get_type() returns null.
 */
-etype_t extract_type (expr_t *e);
+etype_t extract_type (expr_t *e) __attribute__((pure));
 
 /**	Create a new expression node.
 

tools/qfcc/source/switch.c

@@ -85,7 +85,7 @@ get_hash (const void *_cl, void *unused)
 	return Hash_Buffer (&val->v, sizeof (val->v)) + val->lltype;
 }
 
-static int
+static int __attribute__((pure))
 compare (const void *_cla, const void *_clb, void *unused)
 {
 	case_label_t *cla = (case_label_t *) _cla;