common,cli,wrappers,retrace,gui: Use #pragma once.

Smaller footprint, and simplifies refactoring.
diff --git a/common/trace_parser.hpp b/common/trace_parser.hpp
index b0e9753..0dfaabe 100644
--- a/common/trace_parser.hpp
+++ b/common/trace_parser.hpp
@@ -23,8 +23,7 @@
  *
  **************************************************************************/
 
-#ifndef _TRACE_PARSER_HPP_
-#define _TRACE_PARSER_HPP_
+#pragma once
 
 
 #include <iostream>
@@ -223,4 +222,3 @@
 
 } /* namespace trace */
 
-#endif /* _TRACE_PARSER_HPP_ */