fix a few compilation warnings

- remove unused variables and class fields
 - add support for gcc 4.5 & clang's __builtin_unreachable
 - fix 2 bugs related to strict aliasing
 - remove a few unused function parameters

Signed-off-by: Nuno Lopes <t-nclaud@microsoft.com>

src/ast/substitution/matcher.cpp

@@ -18,10 +18,6 @@ Revision History:
 --*/
 #include"matcher.h"
 
-matcher::matcher(ast_manager & m):
-    m_manager(m) {
-}
-
 bool matcher::operator()(expr * e1, expr * e2, substitution & s) {
     reset();
     m_subst = &s;

src/ast/substitution/matcher.h

@@ -30,7 +30,6 @@ class matcher {
     typedef pair_hash<obj_ptr_hash<expr>, obj_ptr_hash<expr> > expr_pair_hash;
     typedef hashtable<expr_pair, expr_pair_hash, default_eq<expr_pair> > cache;
 
-    ast_manager &         m_manager;
     substitution *        m_subst;
     // cache                 m_cache;
     svector<expr_pair>    m_todo;
@@ -38,7 +37,7 @@ class matcher {
     void reset();
 
 public:
-    matcher(ast_manager & m);
+    matcher() {}
 
     /**
        \brief Return true if e2 is an instance of e1.

src/ast/substitution/substitution.cpp

@@ -148,7 +148,7 @@ void substitution::apply(unsigned num_actual_offsets, unsigned const * deltas, e
                     expr * arg     = to_app(e)->get_arg(i);
                     expr * new_arg;
                     
-                    m_apply_cache.find(expr_offset(arg, off), new_arg);
+                    VERIFY(m_apply_cache.find(expr_offset(arg, off), new_arg));
                     new_args.push_back(new_arg);
                     if (arg != new_arg)
                         has_new_args = true;