[build] fix a build break

src/lnav_config.cc

@@ -31,7 +31,10 @@
 
 #include "config.h"
 
+#include <stdio.h>
 #include <assert.h>
+#include <stdlib.h>
+#include <string.h>
 #include <sys/stat.h>
 
 #include "lnav_config.hh"