Compatibility with gcc-4.3

Add "include" to fix error with abort() in dup_expr.cc
Add "include" to AStatement.h so usage of struct PExpr works
Get rid of eval_tree.cc:577: warning: suggest parentheses around comparison in operand of ^

AStatement.h

@@ -22,6 +22,7 @@
 # include  <map>
 # include  "StringHeap.h"
 # include  "LineInfo.h"
+# include  "PExpr.h"
 
 class PExpr;
 

dup_expr.cc

@@ -21,6 +21,7 @@
 
 # include  "netlist.h"
 # include  <cassert>
+# include  <stdlib.h>
 # include  "ivl_assert.h"
 
 NetEAccess* NetEAccess::dup_expr() const

eval_tree.cc

@@ -574,7 +574,7 @@ NetEConst* NetEBComp::eval_eqeq_real_(NetExpr*le, NetExpr*ri, bool ne_flag)
 	    assert(0);
       }
 
-      verinum result((lv == rv ^ ne_flag) ? verinum::V1 : verinum::V0, 1);
+      verinum result(((lv == rv) ^ ne_flag) ? verinum::V1 : verinum::V0, 1);
       vtmp = new NetEConst(result);
       vtmp->set_line(*this);