fix includes with help from include-what-you-use

examples/perplexity/perplexity.cpp

@@ -1,13 +1,20 @@
 #include "common.h"
 #include "llama.h"
 
+#include <algorithm>
+#include <chrono>
 #include <cmath>
 #include <cstdio>
 #include <cstring>
 #include <ctime>
-#include <sstream>
-#include <thread>
+#include <iterator>
 #include <mutex>
+#include <random>
+#include <sstream>
+#include <string>
+#include <thread>
+#include <tuple>
+#include <utility>
 #include <vector>
 
 #if defined(_MSC_VER)