fix regression for simplifying tails with quantifiers, add some more handling for quantified tails

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/muz_qe/expr_safe_replace.h

@@ -0,0 +1,43 @@
+/*++
+Copyright (c) 2012 Microsoft Corporation
+
+Module Name:
+
+    expr_safe_replace.h
+
+Abstract:
+
+    Version of expr_replace/expr_substitution that is safe for quantifiers.
+    
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2012-11-30
+
+Revision History:
+
+
+--*/
+
+#ifndef __EXPR_SAFE_REPLACE_H__
+#define __EXPR_SAFE_REPLACE_H__
+
+#include "ast.h"
+
+class expr_safe_replace {
+    ast_manager& m;
+    expr_ref_vector m_src;
+    expr_ref_vector m_dst;
+    obj_map<expr, expr*> m_subst;
+
+public:
+    expr_safe_replace(ast_manager& m): m(m), m_src(m), m_dst(m) {}
+
+    void insert(expr* src, expr* dst);
+
+    void operator()(expr_ref& e) { (*this)(e.get(), e); }
+
+    void operator()(expr* src, expr_ref& e);
+};
+
+#endif /* __EXPR_SAFE_REPLACE_H__ */