fix: avoid using namespace std; in header files

using directive in a header file is a bad practice because it may lead
to unexpected results.

https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rs-using-directive

parser/parser_policy.c

@@ -45,6 +45,7 @@
 #endif
 #define NPDEBUG(fmt, args...)	/* Do nothing */
 
+using namespace std;
 
 ProfileList policy_list;