Fix potential segfaults at restore related to ctime().

In some games, restore() passes the result of ctime() to mvprintw() or
some other variadic message-formatting function.  If ctime() has not
been declared properly, its return type is inferred to be int instead
of char *.  This does not cause a warning because the compiler does not
know the correct type of variadic arguments.

On platforms where ints and pointers are not the same size, this can,
probably depending on alignment, result in a segfault that is not easy
to trace.

Including time.h fixes the problem.  Some games manually declared
ctime() and avoided the bug.  These declarations have also been
replaced with the include.

arogue5/save.c

@@ -21,6 +21,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <signal.h>
+#include <time.h>
 #include "rogue.h"
 
 bool save_file(FILE *savef);