[clang-tidy] Switch C headers to C++ ones

Found using modernize-return-braced-init-list

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/recur.cpp

@@ -30,13 +30,13 @@
 #include <fstream>
 #include <sstream>
 #include <sys/types.h>
-#include <inttypes.h>
-#include <stdio.h>
-#include <string.h>
+#include <cinttypes>
+#include <cstdio>
+#include <cstring>
 #include <unistd.h>
-#include <stdlib.h>
+#include <cstdlib>
 #include <pwd.h>
-#include <time.h>
+#include <ctime>
 #include <Context.h>
 #include <Lexer.h>
 #include <Datetime.h>