Clean up some sloppy include guards that were clashing with other Boost projects

include/boost/system/windows_error.hpp

@@ -7,8 +7,8 @@
 
 //  See library home page at http://www.boost.org/libs/system
 
-#ifndef BOOST_WINDOWS_ERROR_HPP
-#define BOOST_WINDOWS_ERROR_HPP
+#ifndef BOOST_SYSTEM_WINDOWS_ERROR_HPP
+#define BOOST_SYSTEM_WINDOWS_ERROR_HPP
 
 //  This header is effectively empty for compiles on operating systems where
 //  it is not applicable.
@@ -123,4 +123,4 @@ namespace boost
 
 #endif  // BOOST_WINDOWS_API
 
-#endif  // BOOST_WINDOWS_ERROR_HPP
+#endif  // BOOST_SYSTEM_WINDOWS_ERROR_HPP