include cleanup using iwyu

src/util/Error.hxx

@@ -24,6 +24,7 @@
 #include "Compiler.h"
 
 #include <string>
+#include <utility>
 
 #include <assert.h>
 

src/util/FormatString.cxx

@@ -19,10 +19,13 @@
 
 #include "FormatString.hxx"
 
-#include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
 
+#ifdef WIN32
+#include <string.h>
+#endif
+
 char *
 FormatNewV(const char *fmt, va_list args)
 {

src/util/Tokenizer.cxx

@@ -26,9 +26,6 @@
 
 #include <glib.h>
 
-#include <assert.h>
-#include <string.h>
-
 static constexpr Domain tokenizer_domain("tokenizer");
 
 static inline bool