Replace build_unique with make_unique

This was a rarely used convenience function from when we did not yet
have c++17 support.

src/util.h

@@ -563,15 +563,6 @@ void bro_strerror_r(int bro_errno, char* buf, size_t buflen);
  */
 char* zeekenv(const char* name);
 
-/**
- * Small convenience function. Does what std::make_unique does in C++14. Will not
- * work on arrays.
- */
-template <typename T, typename ... Args>
-std::unique_ptr<T> build_unique (Args&&... args) {
-	return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
-}
-
 /**
  * Escapes bytes in a string that are not valid UTF8 characters with \xYY format. Used
  * by the JSON writer and BIF methods.