Update is_palindrome.hpp

include/boost/algorithm/is_palindrome.hpp

@@ -113,7 +113,7 @@ bool is_palindrome(const R& range, Predicate p)
 /// \note This function will return true for empty sequences and for palindromes.
 ///     For other sequences function will return false.
 ///     Complexity: O(N).
-bool is_palindrome(const char* str)
+inline bool is_palindrome(const char* str)
 {
     if(!str)
 	    return true;