Make sure all headers do #pragma once. (#6188)

src/ast/rewriter/bit_blaster/bit_blaster_tpl_def.h

@@ -16,6 +16,8 @@ Author:
 Revision History:
 
 --*/
+#pragma once
+
 #include "util/rational.h"
 #include "util/common_msgs.h"
 #include "ast/rewriter/bit_blaster/bit_blaster_tpl.h"

src/ast/rewriter/poly_rewriter_def.h

@@ -16,6 +16,7 @@ Author:
 Notes:
 
 --*/
+#pragma once
 
 #include "util/container_util.h"
 #include "ast/rewriter/poly_rewriter.h"

src/ast/rewriter/rewriter_def.h

@@ -16,6 +16,8 @@ Author:
 Notes:
 
 --*/
+#pragma once
+
 #include "ast/rewriter/rewriter.h"
 #include "ast/ast_smt2_pp.h"
 #include "ast/ast_ll_pp.h"